clozapine and Disease-Models--Animal

Schizophrenia is an incurable neuropsychiatric disorder managed mostly by treatment of the patients with antipsychotics. However, the efficacy of these drugs has remained only low to moderate despite intensive research efforts since the early 1950s when chlorpromazine, the first antipsychotic, was synthesized. In addition, antipsychotic treatment can produce often undesired severe side effects in the patients and addressing these remains a large unmet clinical need. One of the reasons for the low effectiveness of these drugs is the limited knowledge about the molecular mechanisms of schizophrenia, which impairs the development of new and more effective treatments. Recently, proteomic studies of clinical and preclinical samples have identified changes in the levels of specific proteins in response to antipsychotic treatment, which have converged on molecular pathways such as cell communication and signaling, inflammation and cellular growth, and maintenance. The findings of these studies are summarized and discussed in this review and we suggest that this provides validation of proteomics as a useful tool for mining drug mechanisms of action and potentially for pinpointing novel molecular targets that may enable development of more effective medications.

Topics: Animals; Antipsychotic Agents; Aripiprazole; Brain; Chlorpromazine; Clozapine; Disease Models, Animal; Gene Expression Regulation; Glycolysis; Humans; Mitochondrial Proteins; Nerve Tissue Proteins; Oxidative Phosphorylation; Proteome; Proteomics; Schizophrenia; Treatment Outcome

Schizophrenia disease models are necessary to elucidate underlying changes and to establish new therapeutic strategies towards a stage where drug efficacy in schizophrenia (against all classes of symptoms) can be predicted. Here we summarise the evidence for a GABA dysfunction in schizophrenia and review the functional neuroanatomy of five pathways implicated in schizophrenia, namely the mesocortical, mesolimbic, ventral striopallidal, dorsal striopallidal and perforant pathways including the role of local GABA transmission and we describe the effect of clozapine on local neurotransmitter release. This review also evaluates psychotropic drug-induced, neurodevelopmental and environmental disease models including their compatibility with brain microdialysis. The validity of disease models including face, construct, etiological and predictive validity and how these models constitute theories about this illness is also addressed. A disease model based on the effect of the abrupt withdrawal of clozapine on GABA release is also described. The review concludes that while no single animal model is entirely successful in reproducing schizophreniform symptomatology, a disease model based on an ability to prevent and/or reverse the abrupt clozapine discontinuation-induced changes in GABA release in brain regions implicated in schizophrenia may be useful for hypothesis testing and for in vivo screening of novel ligands not limited to a single pharmacological class.

Topics: Animals; Antipsychotic Agents; Brain; Clozapine; Disease Models, Animal; gamma-Aminobutyric Acid; Schizophrenia; Schizophrenic Psychology; Synaptic Transmission

Post-mortem investigations have confirmed that glutamatergic NMDA, AMPA, and kainate receptors are involved in the pathophysiology of schizophrenia. It is still unclear, however, whether the altered number of receptors is caused by the disease itself or the medication. Therefore, animal models were investigated for effects of antipsychotic medication after treatment periods of up to 6 months, the results of which are summarized here. Generally, NMDA receptor binding was found to be increased in striatum and nucleus accumbens after therapy with haloperidol, whereas clozapine only increased the number of receptors in nucleus accumbens. While haloperidol led to an increase in AMPA receptors in the posterior cingulate gyrus, striatum, insular cortex, and n. accumbens, clozapine was found to elevate ligand binding in the anterior cingulate gyrus and infralimbic cortex. Although kainate receptor binding was increased in hippocampus by both antipsychotics, clozapine was significantly more effective. In conclusion, data reveal different effects from the typical neuroleptic haloperidol and the atypical antipsychotic clozapine. The results suggest that post-mortem findings in patients with schizophrenia may at least partially be explained by drug effects and plasticity changes induced by long-term medication with antipsychotics.

Topics: Animals; Antipsychotic Agents; Brain; Clozapine; Disease Models, Animal; Haloperidol; Humans; Long-Term Care; Neuronal Plasticity; Neurons; Rats; Receptors, Glutamate; Schizophrenia; Synaptic Transmission

Topics: Animals; Antipsychotic Agents; Cholinergic Agonists; Disease Models, Animal; Dopamine Antagonists; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Humans; Mice; Mice, Transgenic; Nitric Oxide Synthase; Receptor, Serotonin, 5-HT2A; Receptors, AMPA; Receptors, Dopamine D2; Receptors, Dopamine D4; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotensin; Receptors, Serotonin; Schizophrenia; Serotonin Antagonists

It is widely accepted that schizophrenia originates from abnormalities occurring during the early stages of neural development. Although large studies have revealed behavioral precursors of schizophrenia in childhood, the disorder is usually not evident until patients are in their 20s or 30s. Some patients will be resistant to typical antipsychotic treatment at this first-onset of schizophrenia; however, treatment resistance develops in the majority of patients during the course of successive episodes. This ongoing deterioration suggests that a degenerative process operates during the active psychotic phase of the illness. This review presents evidence of neurodevelopmental and neurodegenerative mechanisms for the development of schizophrenia. These data indicate the importance of effective treatment at the first onset of schizophrenia to improve patient outcome. In addition, animal studies suggest that treatment with clozapine may prevent the neurodegenerative component responsible for the development of treatment resistance.

Topics: Animals; Antipsychotic Agents; Brain; Clozapine; Disease Models, Animal; Drug Resistance; Female; Humans; Magnetic Resonance Imaging; Male; Mice; Neurodegenerative Diseases; Pregnancy; Rats; Schizophrenia; Schizophrenic Psychology; Treatment Outcome

The therapeutic success of clozapine and risperidone has focused attention on the interaction between serotonin and dopamine systems as an avenue for superior therapeutics in schizophrenia. The authors review the neurobiological basis for this interaction and its clinical relevance.. The authors synthesized information from more than 100 published articles obtained through electronic and bibliography-directed searches.. The serotonin system inhibits dopaminergic function at the level of the origin of the dopamine system in the midbrain as well as at the terminal dopaminergic fields in the forebrain. Serotonergic antagonists release the dopamine system from this inhibition. This disinhibition of the dopamine system in the striatum may alleviate neuroleptic-induced extrapyramidal symptoms, and a similar disinhibition in the prefrontal cortex may ameliorate negative symptoms. However, the benefits of combined serotonergic-dopaminergic blockade may be observed in only a narrow dose range and may be lost with doses that produce suprathreshold dopaminergic blockade.. Serotonergic modulation of dopaminergic function provides a viable mechanism for enhancing therapeutics in schizophrenia, but much remains unclear. Future research will have to establish the existence of this interaction in humans in vivo, specify the conditions under which it leads to optimal therapeutic benefits, and explore the possibility of using specific serotonergic treatments as flexible adjuncts to typical neuroleptics, rather than the present trend toward using single drugs with combined actions.

Topics: Animals; Antipsychotic Agents; Clinical Trials as Topic; Clozapine; Disease Models, Animal; Dopamine; Dopamine Agents; Drug Interactions; Humans; Mesencephalon; Neural Pathways; Prefrontal Cortex; Prosencephalon; Risperidone; Schizophrenia; Serotonin; Serotonin Agents

This article reviews new medical and surgical treatments for Parkinson's disease (PD). Catechol-O-methyl-transferase (COMT) inhibitors supplement the variety of antiparkinsonian drugs interacting with the dopaminergic system. Clinical studies show that COMT inhibitors prolong the action of levodopa in patients with the "wearing off" phenomenon. The atypical antipsychotic drug clozapine is the treatment of choice for the alleviation of levodopa-induced psychosis. Clozapine also has beneficial effects on tremor and levodopa-induced dyskinesias. Thus, COMT inhibitors and clozapine provide new opportunities for the treatment of patients with longstanding PD and fluctuating responses to levodopa. Experimental evidence in animals suggests that glutamate antagonists have symptomatic and neuroprotective actions in PD. At present, however, only weak antiglutamatergic drugs that have low specificity, such as memantine, amantadine, and budipine are available for clinical studies. Neurotrophic factors, in particular ciliary neurotrophic factor and glial cell line-derived neurotrophic factor, are among the most promising new approaches for neuroprotection in PD. Problems of bioavailability, however, thus far preclude their use in patients. An improved understanding of the pathophysiology of parkinsonism has led to a renaissance of stereotaxic surgery. The subthalamic nucleus is a potential new target for surgical intervention. Ventroposterior pallidotomy has been shown to improve not only rigidity and tremor, but also akinesia. The techniques for thalamic interventions have been refined by introducing chronic thalamic stimulation. Future transplantation approaches to PD will focus on the use of genetically modified cells carrying genes for dopamine-synthesizing enzymes or neurotrophic factors. Animal studies show the feasibility of in vivo gene transfer for the treatment of PD.

Topics: Animals; Antiparkinson Agents; Brain Tissue Transplantation; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Clozapine; Corpus Striatum; Disease Models, Animal; Dopamine Agents; Electric Stimulation; Excitatory Amino Acid Antagonists; Humans; Levodopa; Parkinson Disease; Stereotaxic Techniques; Substantia Nigra; Thalamic Nuclei

Emerging evidence suggests an important role of the human gut microbiome in psychiatry and neurodevelopmental disorders. An increasing body of literature based on animal studies has reported that the gut microbiome influences brain development and behavior by interacting with the gut-brain axis. Furthermore, as the gut microbiome has an important role in metabolism and is known to interact with pharmaceuticals, recent evidence suggests a role for the microbiome in antipsychotic-induced metabolic side effects in animals and humans.. Here we present the protocol for a two-phase study investigating the gut microbiome in healthy controls and in patients with schizophrenia treated with antipsychotics.. Phase I of our study involves humans exclusively. We recruit 25 patients who are chronically treated with clozapine and compare them with 25 healthy controls matched for age, sex, BMI, and smoking status. A second cohort consists of 25 patients newly starting on clozapine, and a third cohort includes 25 antipsychotic-naive patients. The patients in the second cohort and third cohort are prospectively assessed for up to 6 and 12 weeks, respectively. Phase II of this study will incorporate microbiota humanized mouse models to examine the influence of human fecal transplant on metabolic parameters and the gut-brain axis. Progress and Future Directions: We are underway with the first participants enrolled in all phase I treatment cohorts. This study will contribute to elucidating the role of the gut microbiome in schizophrenia and metabolic side effects. In addition, its results may help to explore potential therapeutic targets for antipsychotic-induced metabolic side effects.

Topics: Adult; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Drug-Related Side Effects and Adverse Reactions; Fecal Microbiota Transplantation; Female; Gastrointestinal Microbiome; Humans; Male; Mice; Prospective Studies; Schizophrenia; Weight Gain

Clozapine has long been considered a useful treatment in patients who have schizophrenia with the neuroleptic-induced delayed-onset side effect tardive dyskinesia. We present data in support of the clinical impression using both an animal model of the disorder and dyskinetic patients themselves. Clozapine produces a lower rate of oral dyskinesia in laboratory rats after 6 months of chronic treatment than does haloperidol (8.6 +/- 1.3 vs. 13.6 +/- 1.4 vacuous chewing movements every 5 minutes, respectively), suggesting a lower propensity to cause tardive dyskinesia. In the human, when clozapine was compared with haloperidol in the treatment of patients with tardive dyskinesia, clozapine produced significantly greater benefit for motor symptoms after 12 months of treatment than did haloperidol (p < .001). Moreover, the dyskinesia rebound, which occurred equally in both drug groups at the beginning of the study, was sustained in the haloperidol group but lost in the clozapine-treated patients. These data suggest that dyskinetic patients lose their symptoms of tardive dyskinesia, along with dopaminergic hypersensitivity, with long-term clozapine treatment.

Topics: Adult; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dyskinesia, Drug-Induced; Female; Follow-Up Studies; Haloperidol; Humans; Male; Rats; Schizophrenia; Treatment Outcome

Expression of inhibitory designer receptors exclusively activated by designer drugs (DREADDs) on excitatory hippocampal neurons in the hippocampus represents a potential new therapeutic strategy for drug-resistant epilepsy. To overcome the limitations of the commonly used DREADD agonist clozapine, we investigated the efficacy of the novel DREADD ligand JHU37160 in chemogenetic seizure suppression in the intrahippocampal kainic acid (IHKA) mouse model for temporal lobe epilepsy (TLE). In addition, seizure-suppressing effects of chemogenetics were compared to the commonly used anti-epileptic drug (AED), levetiracetam (LEV). Therefore, an adeno-associated viral vector was injected in the sclerotic hippocampus of IHKA mice to induce expression of a tagged inhibitory DREADD hM4Di or only a tag (control) specifically in excitatory neurons using the CamKIIα promoter. Subsequently, animals were treated with LEV (800 mg/kg), clozapine (0.1 mg/kg), and DREADD ligand JHU37160 (0.1 mg/kg) and the effect on spontaneous seizures was investigated. Clozapine and JHU37160-mediated chemogenetic treatment both suppressed seizures in DREADD-expressing IHKA mice. Clozapine treatment suppressed seizures up to 34 h after treatment, and JHU37160 effects lasted for 26 h after injection. Moreover, both compounds reduced the length of seizures that did occur after treatment up to 28 h and 18 h after clozapine and JHU37160, respectively. No seizure-suppressing effects were found in control animals using these ligands. Chemogenetic seizure treatment suppressed seizures during the first 30 min after injection, and seizures remained suppressed during 8 h following treatment. Chemogenetics thus outperformed effects of levetiracetam (p < 0.001), which suppressed seizure frequency with a maximum of 55 ± 9% for up to 1.5 h (p < 0.05). Only chemogenetic and not levetiracetam treatment affected the length of seizures after treatment (p < 0.001). These results show that the chemogenetic therapeutic strategy with either clozapine or JHU37160 effectively suppresses spontaneous seizures in the IHKA mouse model, confirming JHU37160 as an effective DREADD ligand. Moreover, chemogenetic therapy outperforms the effects of levetiracetam, indicating its potential to suppress drug-resistant seizures.

Topics: Animals; Clozapine; Disease Models, Animal; Kainic Acid; Levetiracetam; Ligands; Mice; Seizures

Amantadine and clozapine have proved to reduce abnormal involuntary movements (AIMs) in preclinical and clinical studies of L-DOPA-Induced Dyskinesias (LID). Even though both drugs decrease AIMs, they may have different action mechanisms by using different receptors and signaling profiles. Here we asked whether there are differences in how they modulate neuronal activity of multiple striatal neurons within the striatal microcircuit at histological level during the dose-peak of L-DOPA in ex-vivo brain slices obtained from dyskinetic mice. To answer this question, we used calcium imaging to record the activity of dozens of neurons of the dorsolateral striatum before and after drugs administration in vitro. We also developed an analysis framework to extract encoding insights from calcium imaging data by quantifying neuronal activity, identifying neuronal ensembles by linking neurons that coactivate using hierarchical cluster analysis and extracting network parameters using Graph Theory. The results show that while both drugs reduce LIDs scores behaviorally in a similar way, they have several different and specific actions on modulating the dyskinetic striatal microcircuit. The extracted features were highly accurate in separating amantadine and clozapine effects by means of principal components analysis (PCA) and support vector machine (SVM) algorithms. These results predict possible synergistic actions of amantadine and clozapine on the dyskinetic striatal microcircuit establishing a framework for a bioassay to test novel antidyskinetic drugs or treatments in vitro.

Topics: Amantadine; Animals; Antiparkinson Agents; Calcium; Clozapine; Corpus Striatum; Disease Models, Animal; Dyskinesia, Drug-Induced; Levodopa; Mice; Neurons; Oxidopamine

Patients with schizophrenia, and rodent models of the disease, both exhibit suppressed neurogenesis, with antipsychotics possibly enhancing neurogenesis in pre-clinical models. Nestin, a cytoskeletal protein, is implicated in neuronal differentiation and adult neurogenesis. We hypothesized that schizophrenia pathogenesis involves nestin downregulation; however, few studies have related nestin to schizophrenia. We assessed nestin protein concentration, prepulse inhibition (PPI), and social interaction in the MK-801 model of schizophrenia, with or without antipsychotic (clozapine) treatment. Adult male Sprague-Dawley rats were intraperitoneally administered saline or MK-801 (0.1 mg/kg) to produce a schizophrenia-like phenotype, with concomitant subcutaneous injections of vehicle or clozapine (5 mg/kg). PPI was assessed on days 1, 8, and 15, and social interaction was assessed on day 4. Hippocampus tissue samples were dissected for Western blotting of nestin concentration. MK-801 alone did not alter nestin concentration, while clozapine alone enhanced hippocampal nestin concentration; this effect was not apparent in animals with MK-801 and clozapine co-administration. MK-801 also produced schizophrenia-like PPI disruptions, some of which were reversed by clozapine. Social interaction deficits were not detected in this model. This is the first report of clozapine-induced enhancements of hippocampal nestin concentration that might be mediated by NMDA receptors. Future studies will explore the impact of neurodevelopmental nestin concentration on symptom onset and antipsychotic treatment.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Hippocampus; Male; Nestin; Rats; Rats, Sprague-Dawley

Topics: Animals; Apnea; Clozapine; Designer Drugs; Disease Models, Animal; Epilepsy; Ligands; Mice; Mice, Transgenic; NAV1.6 Voltage-Gated Sodium Channel; Oxides; Prosencephalon; Seizures; Sudden Unexpected Death in Epilepsy

Cognitive dysfunction is a core feature of schizophrenia that strongly correlates to the patients' difficulties in independent living and occupational functioning. Synaptic dysfunction may result in cognitive and behavioral changes similar to what have been identified in schizophrenia. Shi-Zhen-An-Shen Decoction (SZASD) is the empirical formula of traditional Chinese medicine adopted in treating psychiatric symptoms, especially the cognitive impairment in schizophrenia patients, with proven efficacy in the long term of clinical practice in Beijing Anding Hospital, Capital Medical University. However, the mechanisms of SZASD on the cognitive improvement in schizophrenia is still unclear. Here, we aim to investigate the underlying mechanisms of the impact of SZASD on the cognitive impairment in MK801-induced schizophrenia-like rats.. Six rat groups (n = 12 per group) were subjected to different treatments for 14 days. All the six groups were injected intraperitoneally with a given volume of 0.9% saline and MK801 (0.2 mg/kg) for consecutive 14 days for modelling. And the rats in the SZASD-treated groups and the clozapine-treated group were given SZASD (low, middle, and high doses) or clozapine, respectively, by intragastric administration. Then, we performed behavioral tests after the treatments, and the rats were sacrificed on the 19th day for biological analysis.. Behavioral tests indicated that SZASD mitigated the aberrant motor activity and improved schizophrenia-like rats' spatial reference memory and sensory gating ability. Furthermore, SZASD significantly increased the expressions of PSD95, BDNF, and synapsin I in the hippocampus of MK801-induced schizophrenia-like rats.. Our findings suggest that SZASD may ameliorate cognitive impairment by restoring the levels of synaptic proteins in the hippocampus.

Topics: Animals; Clozapine; Cognitive Dysfunction; Disease Models, Animal; Dizocilpine Maleate; Rats; Schizophrenia

Engineered G protein-coupled receptors (GPCRs) are commonly used in chemogenetics as designer receptors exclusively activated by designer drugs (DREADDs). Although several GPCRs have been studied in astrocytes using a chemogenetic approach, the functional role of the astrocytic G

Topics: Animals; Astrocytes; Brain; Clozapine; Cognitive Dysfunction; Cytokines; Designer Drugs; Disease Models, Animal; GTP-Binding Protein alpha Subunits, Gi-Go; Hippocampus; Lipopolysaccharides; Male; Mice; Mice, Inbred C57BL; Molecular Targeted Therapy; Neuroinflammatory Diseases; Nitric Oxide; Nitric Oxide Synthase Type II; Receptors, G-Protein-Coupled

Although impaired extinction of fear memory (EFM) is a hallmark symptom of posttraumatic stress disorder (PTSD), the mechanisms underlying the impairment are unknown. Activation of the infralimbic cortex (IL) in the medial prefrontal cortex (mPFC) has been reported to predict successful fear extinction, whereas functionally disrupting this region impairs extinction. We examined whether chemogenetic activation of the IL could alleviate impaired EFM in a single prolonged stress (SPS) rat model of PTSD.. Chemogenetic activation of IL and prelimbic (PL) excitatory neurons was undertaken to evaluate EFM using a contextual fear conditioning paradigm. Neuronal activity in the IL was recorded using a 32-multichannel silicon electrode. To examine histological changes in the mPFC, apoptosis was measured by TUNEL staining.. Chemogenetic activation of excitatory neurons in the IL, but not the PL, enhanced EFM in sham rats and resulted in alleviation of EFM impairment in SPS rats. The alleviation of impaired EFM in SPS rats was observed during the extinction test session. Neuronal activity in the IL of SPS rats was lower than that of sham rats after clozapine-n-oxide administration. Increased apoptosis was found in the IL of SPS rats.. These findings suggest that a decreased excitatory response in the IL due, at least in part, to an increase in apoptosis in SPS rats leads to impaired EFM, and that neuronal activation during extinction training could be useful for the treatment of impaired EFM in PTSD patients.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Extinction, Psychological; Fear; Genetic Vectors; Male; Memory; Piperazines; Prefrontal Cortex; Rats; Rats, Sprague-Dawley; Stress Disorders, Post-Traumatic

Chronic methamphetamine (METH) treatment induces behavioral sensitization in rodents. During this process, hyperactivation of the mesolimbic dopamine system plays a central role, and dopamine D2-like receptor-based antipsychotics are known to alleviate the behavioral hyperactivity. The atypical antipsychotic, clozapine (Clz), acts partially as a dopamine D4 receptor (D4R) antagonist and mitigates hyperdopaminergic drug addiction and/or comorbid psychotic symptoms; however, it remains unclear whether D4R blockade contributes to the therapeutic effects of Clz. Here, we evaluated the potential role of D4R in regulating hyperdopaminergia-induced behavioral hyperactivity in METH behavioral sensitization and dopamine transporter (DAT) knockdown (KD) mice. Clz or a D4R-selective antagonist, L-745,870, were co-administered to mice with daily METH in a METH sensitization model, and Clz or L-745,870 were administered alone in a DAT KD hyperactivity model. Locomotor activity and accumbal D4R expression were analyzed. Clz suppressed both the initiation and expression of METH behavioral sensitization, as well as DAT KD hyperactivity. However, repetitive Clz treatment induced tolerance to the suppression effect on METH sensitization initiation. In contrast, D4R inhibition by L-745,870 had no effect on METH sensitization or DAT KD hyperactivity. Accumbal D4R expression was similar between METH-sensitized mice with and without Clz co-treatment. In sum, our results suggest the mesolimbic D4R does not participate in behavioral sensitization encoded by hyperdopaminergia, a finding which likely extends to the therapeutic effects of Clz. Therefore, molecular targets other than D4R should be prioritized in the development of future therapeutics for treatment of hyperdopaminergia-dependent neuropsychiatric disorders.

Topics: Amphetamine-Related Disorders; Animals; Antipsychotic Agents; Behavior, Animal; Central Nervous System Sensitization; Clozapine; Disease Models, Animal; Dopamine Agents; Locomotion; Methamphetamine; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Mice, Knockout; Mice, Transgenic; Psychotic Disorders; Pyridines; Pyrroles; Receptors, Dopamine D4

Clozapine (CLZ) represents an effective treatment for resistant schizophrenia. However, myocarditis, recently reported in about 66% of the psychiatric patients treated with CLZ, has raised concerns about its safety. β-blocking agents have shown to be helpful in the management of myocarditis. Moreover, Vimentin (VIM) and Connexin-43 (CX43) are important structural proteins play key roles in cytoskeletal functions and cellular communication and have complex implications in pathophysiology. The present work aimed to study the mechanisms behind the protective effect of propranolol (PRO) against CLZ-induced myocarditis and the possible involvement of VIM and CX43. The effect of PRO (5 and 10 mg/kg, oral) on the myocarditis induced by CLZ (25 mg/kg/d, i. p.) treatment for 21 days in rats, was assessed biochemically, and immunohistochemically. CLZ treatment increased the serum levels of cardiac injury (CK-MP, LDH and cTn-I) and cardiac levels of oxidative stress (TBARS and NO) markers, proinflammatory cytokines (IL-1β and TNF-α), and mRNA expression of VIM and CX43 with decreased the antioxidant defenses (GSH and GSH-Px). Immunohistochemical study showed increased cardiac expression of VIM, CX43 and caspase-3 proteins. Coadministration of PRO with CLZ, dose-dependently decreased the biochemical and immunohistochemical hallmarks of CLZ-induced myocardial injury and significantly decreased mRNA expression of VIM and CX43. Taken together, our results demonstrate that the cardioprotective effects of PRO on CLZ-induced myocarditis are related in addition to its β-blocking activity to protection of myocardial VIM and CX43 proteins through antagonizing the CLZ-induced oxidative stress and inflammatory response, and preventing cell apoptosis.

Topics: Adrenergic beta-Antagonists; Animals; Antipsychotic Agents; Apoptosis; Cardiotonic Agents; Caspase 3; Clozapine; Connexin 43; Creatine Kinase; Cytokines; Disease Models, Animal; Dose-Response Relationship, Drug; L-Lactate Dehydrogenase; Male; Myocarditis; Myocardium; Oxidative Stress; Propranolol; Rats, Wistar; Troponin I; Vimentin

There is a need to develop animal models of schizophrenia-like behaviors that have both construct and predictive validity. Recently, a neonatal phencyclidine (PCP) and post-weaning social isolation dual-hit model was developed; however, its face and predictive validities need to be further investigated.. The aims of this study were to extend the characterization of the behavioral changes occurring in the neonatal PCP and post-weaning social isolation dual-hit rat model and to evaluate the effects of chronic treatment with clozapine on signs related to schizophrenia.. Male Wistar rat pups were treated with PCP (10 mg/kg s.c.) on postnatal days (PND) 7, 9, and 11. Starting from weaning, neonatal PCP-treated rat pups were socially isolated, while control saline-treated rats were group housed. At adulthood, rats were assessed using behavioral tasks evaluating locomotor activity, social recognition, prepulse inhibition, and reversal learning. Clozapine (3 mg/kg i.p.) was administered daily starting from a week before behavioral tests and until the end of the study.. Neonatal PCP-treated and post-weaning social isolated (PCP-SI) rats displayed persistent and robust locomotor hyperactivity as well as social recognition impairment. The latter could not be explained by variations in the motivation to interact with a juvenile rat. Weak-to-moderate deficits in prepulse inhibition and reversal learning were also observed. Chronic treatment with clozapine attenuated the observed locomotor hyperactivity and social recognition deficits.. The PCP-SI model presents enduring and robust deficits (hyperactivity and social recognition impairment) associated with positive symptoms and cognitive/social deficits of schizophrenia, respectively. These deficits are normalized by chronic treatment with clozapine, thereby confirming the predictive validity of this animal model.

Topics: Animals; Animals, Newborn; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Executive Function; Locomotion; Male; Phencyclidine; Prepulse Inhibition; Rats; Rats, Wistar; Recognition, Psychology; Reversal Learning; Schizophrenia; Schizophrenic Psychology; Social Isolation

One third of epilepsy patients do not become seizure-free using conventional medication. Therefore, there is a need for alternative treatments. Preclinical research using designer receptors exclusively activated by designer drugs (DREADDs) has demonstrated initial success in suppressing epileptic activity. Here, we evaluated whether long-term chemogenetic seizure suppression could be obtained in the intraperitoneal kainic acid rat model of temporal lobe epilepsy, when DREADDs were selectively expressed in excitatory hippocampal neurons.. Epileptic male Sprague Dawley rats received unilateral hippocampal injections of adeno-associated viral vector encoding the inhibitory DREADD hM4D(Gi), preceded by a cell-specific promotor targeting excitatory neurons. The effect of clozapine-mediated DREADD activation on dentate gyrus evoked potentials and spontaneous electrographic seizures was evaluated. Animals were systemically treated with single (.1 mg/kg/24 h) or repeated (.1 mg/kg/6 h) injections of clozapine. In addition, long-term continuous release of clozapine and olanzapine (2.8 mg/kg/7 days) using implantable minipumps was evaluated. All treatments were administered during the chronic epileptic phase and between 1.5 and 13.5 months after viral transduction.. In the DREADD group, dentate gyrus evoked potentials were inhibited after clozapine treatment. Only in DREADD-expressing animals, clozapine reduced seizure frequency during the first 6 h postinjection. When administered repeatedly, seizures were suppressed during the entire day. Long-term treatment with clozapine and olanzapine both resulted in significant seizure-suppressing effects for multiple days. Histological analysis revealed DREADD expression in both hippocampi and some cortical regions. However, lesions were also detected at the site of vector injection.. This study shows that inhibition of the hippocampus using chemogenetics results in potent seizure-suppressing effects in the intraperitoneal kainic acid rat model, even 1 year after viral transduction. Despite a need for further optimization, chemogenetic neuromodulation represents a promising treatment prospect for temporal lobe epilepsy.

Topics: Animals; Anticonvulsants; Clozapine; Dentate Gyrus; Disease Models, Animal; Epilepsy, Temporal Lobe; Evoked Potentials; G-Protein-Coupled Receptor Kinases; Gene Editing; Hippocampus; Male; Olanzapine; Rats; Rats, Sprague-Dawley; Receptors, Neurotransmitter; Seizures

Beyond abnormalities in the neurotransmitter hypothesis, recent evidence suggests that mitochondrial dysfunction and immune-inflammatory responses contribute to the pathophysiology of schizophrenia. The prefrontal cortex (PFC) undergoes maturation and development during adolescence, which is a critical time window in life that is vulnerable to environmental adversities and the development of psychiatric disorders such as schizophrenia. Applying eight weeks of post-weaning social isolation stress (PWSI) to rats, as an animal model of schizophrenia, we decided to investigate the effects of PWSI on the mitochondrial function and expression of immune-inflammatory genes in the PFC of normal and stressed rats. To do this, control and PWSI rats were divided into treatment (clozapine; CLZ, 2.5 mg/kg/day for 28 days) and non-treatment sub-groups. Our results showed PWSI caused schizophrenic-like behaviors in rats and induced mitochondrial dysfunction as well as upregulation of genes associated with innate immunity in the PFC. Chronic treatment with CLZ attenuated the effects of PWSI on behavioral abnormalities, mitochondrial dysfunction, and immune-inflammatory responses in the PFC of rats. These results may advance our understanding about the mechanism of action of CLZ that targets mitochondrial dysfunction and immune-inflammatory responses as factors involved in the pathophysiology of schizophrenia.

Topics: Anhedonia; Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Gene Expression; Inflammation; Male; Mitochondria; Motivation; Nesting Behavior; Open Field Test; Prefrontal Cortex; Rats; Schizophrenia; Schizophrenic Psychology; Social Interaction; Social Isolation

MiRNAs are small, non-coding RNAs that can silence the expression of various target genes by binding their mRNAs and thus regulate a wide range of crucial bodily functions. However, the miRNA expression profile of schizophrenia after antipsychotic mediation is largely unknown. Non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonists such as MK-801 have provided useful animal models to investigate the effects of schizophrenia-like symptoms in rodent animals. Herein, the hippocampal miRNA expression profiles of Sprague-Dawley rats pretreated with MK-801 were examined after antipsychotic clozapine (CLO) treatment. Total hippocampal RNAs from three groups were subjected to next-generation sequencing (NGS), and bioinformatics analyses, including differential expression and enrichment analyses, were performed. Eight miRNAs were differentially expressed between the MK-801 and vehicle (VEH) control groups. Interestingly, 14 miRNAs were significantly differentially expressed between the CLO + MK-801 and MK-801 groups, among which rno-miR-184 was the most upregulated. Further analyses suggested that these miRNAs modulate target genes that are involved in endocytosis regulation, ubiquitin-mediated proteolysis, and actin cytoskeleton regulation and thus might play important roles in the pathogenesis of schizophrenia. Our results suggest that differentially expressed miRNAs play important roles in the complex pathophysiology of schizophrenia and subsequently impact brain functions.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Exploratory Behavior; Gene Expression; Hippocampus; Male; MicroRNAs; Rats; Rats, Sprague-Dawley; Schizophrenia

In the mammalian hippocampus, adult-born granule cells (abGCs) contribute to the function of the dentate gyrus (DG). Disruption of the DG circuitry causes spontaneous recurrent seizures (SRS), which can lead to epilepsy. Although abGCs contribute to local inhibitory feedback circuitry, whether they are involved in epileptogenesis remains elusive. Here, we identify a critical window of activity associated with the aberrant maturation of abGCs characterized by abnormal dendrite morphology, ectopic migration, and SRS. Importantly, in a mouse model of temporal lobe epilepsy, silencing aberrant abGCs during this critical period reduces abnormal dendrite morphology, cell migration, and SRS. Using mono-synaptic tracers, we show silencing aberrant abGCs decreases recurrent CA3 back-projections and restores proper cortical connections to the hippocampus. Furthermore, we show that GABA-mediated amplification of intracellular calcium regulates the early critical period of activity. Our results demonstrate that aberrant neurogenesis rewires hippocampal circuitry aggravating epilepsy in mice.

Topics: Animals; Calcium; Clozapine; Disease Models, Animal; Electroencephalography; Epilepsy; Epilepsy, Temporal Lobe; Female; gamma-Aminobutyric Acid; Hippocampus; Mice, Inbred C57BL; Mice, Transgenic; Neurogenesis; Neurons; Pilocarpine; Retroviridae; Seizures

Progressive multiple sclerosis is characterized by chronic inflammation with microglial activation, oxidative stress, accumulation of iron and continuous neurodegeneration with inadequate effectiveness of medications used so far. We now investigated effects of iron on microglia and used the previously identified neuroprotective antipsychotic clozapine. Microglia were treated with iron and clozapine followed by analysis of cell death and response to oxidative stress, cytokine release and neuronal phagocytosis. Clozapine was investigated in chronic EAE regarding optimal dosing and therapeutic effectiveness in different treatment paradigms. Animals were scored clinically by blinded raters. Spinal cords were analyzed histologically for inflammation, demyelination, microglial activation and iron accumulation and for transcription changes of regulators of iron metabolism and inflammation. Effects on immune cells were analyzed using flow cytometry.. Iron impaired microglial function. Clozapine regulates microglial function and attenuates chronic EAE, even in a therapeutic treatment paradigm. This well-defined generic medication might therefore be considered as promising add-on therapeutic for further development in progressive MS.

Topics: Animals; Antipsychotic Agents; Biomarkers; Cell Line; Chronic Disease; Clozapine; Cytokines; Disease Models, Animal; Dose-Response Relationship, Drug; Encephalomyelitis, Autoimmune, Experimental; Humans; Immunomodulation; Inflammation Mediators; Mice; Microglia; Oxidative Stress; Phagocytosis; Treatment Outcome

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease characterized by myelin damage followed by axonal and ultimately neuronal loss. The etiology and physiopathology of MS are still elusive, and no fully effective therapy is yet available. We investigated the role in MS of autophagy (physiologically, a controlled intracellular pathway regulating the degradation of cellular components) and of mitophagy (a specific form of autophagy that removes dysfunctional mitochondria). We found that the levels of autophagy and mitophagy markers are significantly increased in the biofluids of MS patients during the active phase of the disease, indicating activation of these processes. In keeping with this idea, in vitro and in vivo MS models (induced by proinflammatory cytokines, lysolecithin, and cuprizone) are associated with strongly impaired mitochondrial activity, inducing a lactic acid metabolism and prompting an increase in the autophagic flux and in mitophagy. Multiple structurally and mechanistically unrelated inhibitors of autophagy improved myelin production and normalized axonal myelination, and two such inhibitors, the widely used antipsychotic drugs haloperidol and clozapine, also significantly improved cuprizone-induced motor impairment. These data suggest that autophagy has a causal role in MS; its inhibition strongly attenuates behavioral signs in an experimental model of the disease. Therefore, haloperidol and clozapine may represent additional therapeutic tools against MS.

Topics: Animals; Antipsychotic Agents; Autophagy; Autophagy-Related Proteins; Axons; Biomarkers; Clozapine; Cytokines; Demyelinating Diseases; Disease Models, Animal; Glucose; Haloperidol; Inflammation; Interleukin-1beta; Mitochondria; Mitophagy; Models, Biological; Motor Activity; Multiple Sclerosis; Myelin Basic Protein; Myelin Sheath; Stress, Physiological; Tumor Necrosis Factor-alpha

Clozapine is widely employed in the treatment of schizophrenia. Compared with that of atypical first-generation antipsychotics, atypical second-generation antipsychotics such as clozapine have less severe side effects and may positively affect obesity and blood glucose level. However, no systematic study of clozapine's adverse metabolic effects-such as changes in kidney and liver function, body weight, glucose and triglyceride levels, and retinopathy-was conducted. This research investigated how clozapine affects weight, the bodily distribution of chromium, liver damage, fatty liver scores, glucose homeostasis, renal impairment, and retinopathy in mice fed a high fat diet (HFD). We discovered that obese mice treated with clozapine gained more weight and had greater kidney, liver, and retroperitoneal and epididymal fat pad masses; higher daily food efficiency; higher serum or hepatic triglyceride, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, and creatinine levels; and higher hepatic lipid regulation marker expression than did the HFD-fed control mice. Furthermore, the clozapine group mice exhibited insulin resistance, poorer insulin sensitivity, greater glucose intolerance, and less Akt phosphorylation; their GLUT4 expression was lower, they had renal damage, more reactive oxygen species, and IL-1 expression, and, finally, their levels of antioxidative enzymes (superoxide dismutase, glutathione peroxidase, and catalase) were lower. Moreover, clozapine reduced the thickness of retinal cell layers and increased

Topics: Adipocytes; Animals; Biomarkers; Body Weights and Measures; Chromium; Clozapine; Disease Models, Animal; Fatty Acid-Binding Proteins; Fluorescent Antibody Technique; Gene Expression; Gene Expression Regulation; Glucose Intolerance; Immunohistochemistry; Insulin; Kidney Diseases; Liver; Mice; Mice, Obese; Nitric Oxide Synthase Type II; Non-alcoholic Fatty Liver Disease; Obesity; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Retinal Diseases; Sterol Regulatory Element Binding Protein 1

Numerous human clinical studies have suggested that decreased locomotor activity is a common symptom of major depressive disorder (MDD), as well as other psychiatric diseases. In MDD, the midbrain ventral tegmental area (VTA) dopamine (DA) neurons are closely related to regulate the information processing of reward, motivation, cognition, and aversion. However, the neural circuit mechanism that underlie the relationship between VTA-DA neurons and MDD-related motor impairments, especially hypolocomotion, is still largely unknown. Herein, we investigate how the VTA-DA neurons contribute to the hypolocomotion performance in chronic social defeat stress (CSDS), a mouse model of depression-relevant neurobehavioral states. The results show that CSDS could affect the spontaneous locomotor activity of mice, but not the grip strength and forced locomotor ability. Chemogenetic activation of VTA-DA neurons alleviated CSDS-induced hypolocomotion. Subsequently, quantitative whole-brain mapping revealed decreased projections from VTA-DA neurons to substantia nigra pars reticulata (SNr) after CSDS treatment. Optogenetic activation of dopaminergic projection from VTA to SNr with the stimulation of phasic firing, but not tonic firing, could significantly increase the locomotor activity of mice. Moreover, chemogenetic activation of VTA-SNr dopaminergic circuit in CSDS mice could also rescued the decline of locomotor activity. Taken together, our data suggest that the VTA-SNr dopaminergic projection mediates CSDS-induced hypolocomotion, which provides a theoretical basis and potential therapeutic target for MDD.

Topics: Animals; Channelrhodopsins; Chronic Disease; Clozapine; Depressive Disorder, Major; Disease Models, Animal; Dopamine; Dopaminergic Neurons; Genes, Reporter; Genetic Vectors; Hand Strength; Locomotion; Male; Mice; Mice, Inbred C57BL; Neural Pathways; Optogenetics; Pars Reticulata; Receptor, Muscarinic M3; Recombinant Proteins; Rotarod Performance Test; Social Defeat; Stress, Psychological; Tyrosine 3-Monooxygenase; Ventral Tegmental Area

The low efficacy of antipsychotic drugs (e.g., clozapine) for negative symptoms and cognitive impairment has led to the introduction of adjuvant therapies. Because previous data suggest the procognitive potential of the antidiabetic drug metformin, this study aimed to assess the effects of chronic clozapine and metformin oral administration (alone and in combination) on locomotor and exploratory activities and cognitive function in a reward-based test in control and a schizophrenia-like animal model (Wisket rats). As impaired dopamine D1 receptor (D

Topics: Animals; Behavior, Animal; Body Weight; Clozapine; Disease Models, Animal; Drug Interactions; Feeding Behavior; Metformin; Receptors, Dopamine D1; RNA, Messenger; Schizophrenia; Time Factors

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

Oxytocin (OT) is critical for the expression of social behavior across a wide array of species; however, the role of this system in the encoding of socially relevant information is not well understood. In the present study, we show that chemogenetic activation of OT neurons within the paraventricular nucleus of the hypothalamus (PVH) of male mice (OT-Ires-Cre) enhanced social investigation during a social choice test, while chemogenetic inhibition of these neurons abolished typical social preferences. These data suggest that activation of the OT system is necessary to direct behavior preferentially toward social stimuli. To determine whether the presence of a social stimulus is sufficient to induce activation of PVH-OT neurons, we performed the first definitive recording of OT neurons in awake mice using two-photon calcium imaging. These recordings demonstrate that social stimuli activate PVH-OT neurons and that these neurons differentially encode social and nonsocial stimuli, suggesting that PVH-OT neurons may act to convey social salience of environmental stimuli. Finally, an attenuation of social salience is associated with social disorders, such as autism. We therefore also examined possible OT system dysfunction in a mouse model of autism,

Topics: Action Potentials; Animals; Appetitive Behavior; Autistic Disorder; Benzodiazepines; Calcium Signaling; Clozapine; Disease Models, Animal; Exploratory Behavior; Genes, Reporter; Male; Mice; Mice, Knockout; Microfilament Proteins; Nerve Tissue Proteins; Neurons; Oxytocin; Paraventricular Hypothalamic Nucleus; Patch-Clamp Techniques; Pyrazoles; Receptors, Oxytocin; Social Behavior; Wakefulness

Schizophrenia is a chronic, disabling and one of the major neurological illnesses affecting nearly 1% of the global population. Currently available antipsychotic medications possess limited effects. The current research aimed at investigating potential therapeutic add-on benefit to enhance the effects of clozapine anti-schizophrenic.. To induce schizophrenia, ketamine was administered at a dose of 25 mg/kg i.p. for 14 consecutive days. Naringin was administered to Wistar rats at a dose of 100 mg/kg orally, alone or in combination with clozapine 5 mg/kg i.p from day 8 to day 14. Furthermore, behavioral tests were conducted to evaluate positive, negative and cognitive symptoms of schizophrenia. In addition, neurotransmitters' levels were detected using HPLC. Moreover, oxidative stress markers were assessed using spectrophotometry. Furthermore, apoptotic and wnt/β-catenin pathway markers were determined using western blotting (Akt, GSK-3β and β-catenin), colorimetric methods (Caspase-3) and immunohistochemistry (Bax, Bcl2 and cytochrome c).. Ketamine induced positive, negative and cognitive schizophrenia symptoms together with neurotransmitters' imbalance. In addition, ketamine treatment caused significant glutathione depletion, lipid peroxidation and reduction in catalase activity. Naringin and/or clozapine treatment significantly attenuated ketamine-induced schizophrenic symptoms and oxidative injury. Additionally, ketamine provoked apoptosis via increasing Bax/Bcl2 expression, caspase-3 activity, and Cytochrome C and Akt protein expression while naringin/clozapine treatment significantly inhibited this apoptotic effect. Moreover, naringin activated the neurodevelopmental wnt/β-catenin signaling pathway evidenced by increasing pGSK-3β and reducing pβ-catenin protein expression.. These findings may suggest that naringin possesses a potential therapeutic add-on effect against ketamine-induced schizophrenia.

Topics: Animals; Antipsychotic Agents; beta Catenin; Clozapine; Disease Models, Animal; Flavanones; Glycogen Synthase Kinase 3 beta; Ketamine; Male; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Schizophrenia; Signal Transduction; Wnt Proteins

Schizophrenia is a common psychiatric disease that cannot be fully treated with current antipsychotic drugs. It has shown that glutamatergic NMDA receptor antagonists such as MK-801 cause schizophrenia-like phenotype in rodents. Recent studies indicated that α7 nicotinic acetylcholine receptor (nAChR) deficits contribute to schizophrenia. Enhancing its activity with agonist or positive allosteric modulators (PAMs) may be a valuable approach for treatment. The certain intracellular pathways such as Akt/Glycogen synthase kinase 3 beta (GSK-3β) and phosphodiesterase-4 (PDE-4)/cAMP are associated with the pathogenesis of schizophrenia. In this study, we examined the effect of α7 nAChR agonists and PAMs on the behavioral and molecular phenotype of schizophrenia in the subchronic MK-801 administered rats. Social interaction, the levels of α7 nAChR, and related intracellular pathways (cAMP, PDE4A, PDE4D, p-Akt/Akt, p-GSK-3β/GSK-3β) were measured by behavioral or ELISA and western blot tests. Subchronic MK-801 administration decreased the following behaviors and increased the avoiding behaviors. However, only α7 nAChR agonist (A-582941) increased the following behavior while α7 nAChR agonist, PAMs (CCMI and PNU-120596), and clozapine decreased the avoiding behavior compared to MK-801. For molecular parameters, MK-801 administration decreased the α7 nAChR, p-Akt/Akt, p-GSK-3β/GSK-3β expressions, and cAMP levels while it increased PDE4A, PDE4D expressions in the prefrontal cortex. Besides, MK-801 decreased the α7 nAChR, p-GSK-3β/GSK-3β expressions in the hippocampus. We found clozapine, α7 nAChR agonists, and PAMs reversed the molecular deficits induced by MK-801. Herein, we showed that prefrontal cortex is more sensitive to the devastating effects of subchronic MK-801 administration, especially for PDE4, in rats. In addition to clozapine, α7 nAChR agonists and PAMs found to be beneficial on both social and molecular deficits induced by MK-801 in rats. We suggested that α7 nAChR agonists and PAMs might be valuable approaches to treat negative symptoms of schizophrenia when unmet needs and current limitations considered in this pathology.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Allosteric Regulation; alpha7 Nicotinic Acetylcholine Receptor; Animals; Avoidance Learning; Clozapine; Cyclic AMP; Cyclic Nucleotide Phosphodiesterases, Type 4; Disease Models, Animal; Dizocilpine Maleate; Glycogen Synthase Kinase 3 beta; Isoxazoles; Male; Phenylurea Compounds; Prefrontal Cortex; Proto-Oncogene Proteins c-akt; Pyridazines; Pyrroles; Rats; Rats, Wistar; Schizophrenia; Signal Transduction; Social Interaction; Treatment Outcome

Trigeminal neuralgia (TN) is debilitating and is usually accompanied by mood disorders. The lateral habenula (LHb) is considered to be involved in the modulation of pain and mood disorders, and the present study aimed to determine if and how the LHb participates in the development of pain and anxiety in TN. To address this issue, a mouse model of partial transection of the infraorbital nerve (pT-ION) was established. pT-ION induced stable and long-lasting primary and secondary orofacial allodynia and anxiety-like behaviors that correlated with the increased excitability of LHb neurons. Adeno-associated virus (AAV)-mediated expression of hM4D(Gi) in glutamatergic neurons of the unilateral LHb followed by clozapine-N-oxide application relieved pT-ION-induced anxiety-like behaviors but not allodynia. Immunofluorescence validated the successful infection of AAV in the LHb, and microarray analysis showed changes in gene expression in the LHb of mice showing allodynia and anxiety-like behaviors after pT-ION. Among these differentially expressed genes was Tacr3, the downregulation of which was validated by RT-qPCR. Rescuing the downregulation of Tacr3 by AAV-mediated Tacr3 overexpression in the unilateral LHb significantly reversed pT-ION-induced anxiety-like behaviors but not allodynia. Whole-cell patch clamp recording showed that Tacr3 overexpression suppressed nerve injury-induced hyperexcitation of LHb neurons, and western blotting showed that the pT-ION-induced upregulation of p-CaMKII was reversed by AAV-mediated Tacr3 overexpression or chemicogenetic inhibition of glutamatergic neurons in the LHb. Moreover, not only anxiety-like behaviors, but also allodynia after pT-ION were significantly alleviated by chemicogenetic inhibition of bilateral LHb neurons or by bilateral Tacr3 overexpression in the LHb. In conclusion, Tacr3 in the LHb plays a protective role in treating trigeminal nerve injury-induced allodynia and anxiety-like behaviors by suppressing the hyperexcitability of LHb neurons. These findings provide a rationale for suppressing unilateral or bilateral LHb activity by targeting Tacr3 in treating the anxiety and pain associated with TN.

Topics: Animals; Antipsychotic Agents; Anxiety; Behavior, Animal; Clozapine; Disease Models, Animal; Elevated Plus Maze Test; Glutamic Acid; Habenula; Hyperalgesia; Maxillary Nerve; Mice; Neural Inhibition; Neurons; Open Field Test; Receptors, Neurokinin-3; Transcriptome; Trigeminal Neuralgia

Older persons and, more severely, persons with Parkinson's disease (PD) exhibit gait dysfunction, postural instability and a propensity for falls. These dopamine (DA) replacement-resistant symptoms are associated with losses of basal forebrain and striatal cholinergic neurons, suggesting that falls reflect disruption of the corticostriatal transfer of movement-related cues and their striatal integration with movement sequencing. To advance a rodent model of the complex movement deficits of Parkinsonian fallers, here we first demonstrated that male and female rats with dual cortical cholinergic and striatal DA losses (DL rats) exhibit cued turning deficits, modeling the turning deficits seen in these patients. As striatal cholinergic interneurons (ChIs) are positioned to integrate movement cues with gait, and as ChI loss has been associated with falls in PD, we next used this task, as well as a previously established task used to reveal heightened fall rates in DL rats, to broadly test the role of ChIs. Chemogenetic inhibition of ChIs in otherwise intact male and female rats caused cued turning deficits and elevated fall rates. Spontaneous turning was unaffected. Furthermore, chemogenetic stimulation of ChIs in DL rats reduced fall rates and restored cued turning performance. Stimulation of ChIs was relatively more effective in rats with viral transfection spaces situated lateral to the DA depletion areas in the dorsomedial striatum. These results indicate that striatal ChIs are essential for the control of complex movements, and they suggest a therapeutic potential of stimulation of ChIs to restore gait and balance, and to prevent falls in PD.

Topics: Accidental Falls; Animals; Antipsychotic Agents; Clozapine; Cues; Disease Models, Animal; Dopamine; Dopamine Agents; Female; Gait Disorders, Neurologic; Interneurons; Male; Neostriatum; Observer Variation; Parasympathetic Nervous System; Parkinsonian Disorders; Rats

Topics: Acetylcholine; Administration, Oral; Allosteric Regulation; alpha7 Nicotinic Acetylcholine Receptor; Animals; Blood-Brain Barrier; Disease Models, Animal; Drug Design; Evoked Potentials; Half-Life; Humans; Mice; Oocysts; Rats; Schizophrenia; Structure-Activity Relationship; Thiazoles; Xenopus laevis

There is a major clinical need for new therapies for the treatment of chronic itch. Many of the molecular components involved in itch neurotransmission are known, including the neuropeptide NPPB, a transmitter required for normal itch responses to multiple pruritogens in mice. Here, we investigated the potential for a novel strategy for the treatment of itch that involves the inhibition of the NPPB receptor NPR1 (natriuretic peptide receptor 1). Because there are no available effective human NPR1 (hNPR1) antagonists, we performed a high-throughput cell-based screen and identified 15 small-molecule hNPR1 inhibitors. Using in vitro assays, we demonstrated that these compounds specifically inhibit hNPR1 and murine NPR1 (mNPR1). In vivo, NPR1 antagonism attenuated behavioral responses to both acute itch- and chronic itch-challenged mice. Together, our results suggest that inhibiting NPR1 might be an effective strategy for treating acute and chronic itch.

Topics: Animals; Behavior, Animal; Cell-Free System; Dermatitis, Contact; Disease Models, Animal; Ganglia, Spinal; Humans; Mice, Inbred C57BL; Mice, Knockout; Neurons; Pruritus; Receptors, Atrial Natriuretic Factor; Reproducibility of Results; Signal Transduction; Small Molecule Libraries

Perinatal virus infection is an environmental risk factor for neurodevelopmental disorders such as schizophrenia. We previously demonstrated that neonatal treatment with a viral mimetic, polyriboinosinic-polyribocytidilic acid (polyI:C), in mice leads to emotional and cognitive deficits in adolescence. Here, we investigated the effects of antipsychotics on polyI:C-induced behavioral abnormalities. We also performed a proteomic analysis in the hippocampus of polyI:C-treated adult mice using two-dimensional electrophoresis to understand the changes in protein expression following neonatal immune activation. Neonatal mice were subcutaneously injected with polyI:C for 5 days (postnatal day 2-6). At 10 weeks, sensorimotor gating, emotional and cognitive function were analyzed in behavioral tests. Clozapine improved PPI deficit and emotional and cognitive dysfunction in polyI:C-treated mice. However, haloperidol improved only PPI deficit. Proteomic analysis revealed that two candidate proteins were obtained in the hippocampus of polyI:C-treated mice, including aldehyde dehydrogenase family 1 member L1 (ALDH1L1) and collapsin response mediator protein 5 (CRMP5). These data suggest that the neonatal polyI:C-treated mouse model may be useful for evaluating antipsychotic activity of compounds. Moreover, changes in the protein expression of ALDH1L1 and CRMP5 support our previous findings that astrocyte-neuron interaction plays a role in the pathophysiology of neurodevelopmental disorders induced by neonatal immune activation.

Topics: Aldehyde Dehydrogenase 1 Family; Animals; Animals, Newborn; Antipsychotic Agents; Clozapine; Disease Models, Animal; Exploratory Behavior; Female; Haloperidol; Hippocampus; Hydrolases; Interpersonal Relations; Mice; Microtubule-Associated Proteins; Nerve Tissue Proteins; Poly I-C; Pregnancy; Prepulse Inhibition; Proteomics; Recognition, Psychology; Schizophrenia; Sensory Gating

Germinal matrix hemorrhage (GMH), affecting about 1 in 300 births, is a major perinatal disease with lifelong neurological consequences. Yet despite advances in neonatal medicine, there is no effective intervention. GMH is characterized by localized bleeding in the germinal matrix (GM), due to inherent vessel fragility unique to this developing brain region. Studies have shown that reduced TGFβ signaling contributes to this vascular immaturity. We have previously shown that a region-specific G-protein-coupled receptor pathway in GM neural progenitor cells regulates integrin β8, a limiting activator of pro-TGFβ. In this study, we use mice to test whether this regional pathway can be harnessed for GMH intervention. We first examined the endogenous dynamics of this pathway and found that it displays specific patterns of activation. We then investigated the functional effects of altering these dynamics by chemogenetics and found that there is a narrow developmental window during which this pathway is amenable to manipulation. Although high-level activity in this time window interferes with vessel growth, moderate enhancement promotes vessel maturation without compromising growth. Furthermore, we found that enhancing the activity of this pathway in a mouse model rescues all GMH phenotypes. Altogether, these results demonstrate that enhancing neurovascular signaling through pharmacological targeting of this pathway may be a viable approach for tissue-specific GMH intervention. They also demonstrate that timing and level are likely two major factors crucial for success. These findings thus provide critical new insights into both brain neurovascular biology and the intervention of GMH.

Topics: Animals; Blood Vessels; Cerebrovascular Circulation; Clozapine; Disease Models, Animal; Female; Integrin beta Chains; Intracranial Hemorrhages; Mice; Neostriatum; Neural Stem Cells; Receptors, G-Protein-Coupled; Signal Transduction; Transforming Growth Factor beta

Parkinson's disease (PD), classically defined as a progressive motor disorder accompanied with dopaminergic neuron loss and presence of Lewy bodies, is the second most common neurodegenerative disease. PD also has various non-classical symptoms, including cognitive impairments. In addition, inflammation and astrogliosis are recognized as an integral part of PD pathology. The hippocampus (Hipp) is a brain region involved in cognition and memory, and the neuropeptide orexin has been shown to enhance learning and memory. Previous studies show impairments in Hipp-dependent memory in a transgenic mouse model of Parkinson's disease (A53T mice), and we hypothesized that increasing orexin tone will reverse this. To test this, we subjected 3, 5, and 7-month old A53T mice to a Barnes maze and a contextual object recognition test to determine Hipp dependent memory. Inflammation and astrogliosis markers in the Hipp were assessed by immuno-fluorescence densitometry. The data show that early cognitive impairment is coupled with an increase in expression of inflammatory and astrogliosis markers. Next, in two separate experiments, mice were given intra-hippocampal injections of orexin or chemogenetic viral injections of an orexin neuron specific Designer Receptor Exclusively Activated by Designer Drug (DREADD). For the pharmacological approach mice were intracranially treated with orexin A, whereas the chemogenetic approach utilized clozapine N-oxide (CNO). Both pharmacological orexin A intervention as well as chemogenetic activation of orexin neurons ameliorated Hipp-dependent early memory impairment observed in A53T mice. This study implicates orexin in PD-associated cognitive impairment and suggests that exogenous orexin treatment and/or manipulation of endogenous orexin levels may be a potential strategy for addressing early cognitive loss in PD.

Topics: Animals; Calcium-Binding Proteins; Cell Count; Clozapine; Disease Models, Animal; Glial Fibrillary Acidic Protein; Gliosis; Hippocampus; Inflammation; Injections; Male; Maze Learning; Memory Disorders; Mice, Inbred C57BL; Mice, Transgenic; Microfilament Proteins; Orexins; Parkinson Disease; Reproducibility of Results

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Frontal Lobe; Histone Deacetylase 2; Mice; Mice, Knockout; Psychotic Disorders; Receptor, Serotonin, 5-HT2A; Receptors, Metabotropic Glutamate

Isolation rearing produces significant behavioral and neurochemical dysfunctions in rodents, which resemble the symptoms of schizophrenia. Clozapine, one of the atypical antipsychotics, is widely used in the treatment of schizophrenia patients and in experimental studies. In this study, male Sprague Dawley rats were randomly assigned to either group-reared or isolation-reared conditions during postnatal days (PNDs) 21-34. During PNDs 46-55, the rats were subjected to chronic clozapine (1.0 mg/kg for 10 days) or saline treatment. On PND 56, all rats underwent behavioral testing and then were sacrificed for biochemical testing. The results indicated that adolescent social isolation induced impairments in prepulse inhibition and reversal learning, and clozapine injection improved the prepulse inhibition disruption but not reversal learning ability. Furthermore, clozapine administration reversed the increased brain-derived neurotrophic factor (BDNF) mRNA level in the medial prefrontal cortex (mPFC) that was induced by adolescent isolation. However, clozapine decreased the BDNF mRNA level in the mPFC in group-reared rats. Together, our findings provide additional evidence that a low dose of chronic clozapine treatment could improve information filtering/sensorimotor gating and alterations in the BDNF mRNA level in the mPFC induced by adolescent social isolation.

Topics: Animals; Antipsychotic Agents; Brain-Derived Neurotrophic Factor; Clozapine; Disease Models, Animal; Gene Expression; Learning; Male; Prefrontal Cortex; Prepulse Inhibition; Rats; Rats, Sprague-Dawley; Reflex, Startle; Reversal Learning; RNA, Messenger; Schizophrenia; Social Isolation

Topics: Animals; Antipsychotic Agents; Brain; Brain-Derived Neurotrophic Factor; Cell Adhesion Molecules, Neuronal; Chromatin; Chromatin Assembly and Disassembly; Clozapine; Disease Models, Animal; DNA Methylation; Epigenesis, Genetic; Extracellular Matrix Proteins; Female; Glutamate Decarboxylase; Male; Mental Disorders; Mice; Nerve Tissue Proteins; Phthalimides; Pregnancy; Prenatal Exposure Delayed Effects; Promoter Regions, Genetic; Reelin Protein; Serine Endopeptidases; Tryptophan

Topics: Animals; Antipsychotic Agents; Carnitine; Cell Line; Chemical and Drug Induced Liver Injury; Clozapine; Disease Models, Animal; Dogs; Down-Regulation; Hep G2 Cells; Humans; Inhibitory Concentration 50; Kidney Tubules, Proximal; Lipid Metabolism; Liver; Madin Darby Canine Kidney Cells; Mice; Mice, Inbred ICR; Primary Cell Culture; Renal Reabsorption; Schizophrenia; Solute Carrier Family 22 Member 5; Toxicity Tests, Acute; Toxicity Tests, Chronic

The nuclear distribution element genes are conserved from fungus to humans. The nematode Caenorhabditis elegans expresses two isoforms of nuclear distribution element genes, namely nud-1 and nud-2. While nud-1 was functionally demonstrated to be the worm nudC ortholog, bioinformatic analysis revealed that the nud-2 gene encodes the worm ortholog of the mammalian NDE1 (Nuclear Distribution Element 1 or NudE) and NDEL1 (NDE-Like 1 or NudEL) genes, which share overlapping roles in brain development in mammals and also mediate the axon guidance in mammalian and C. elegans neurons. A significantly higher NDEL1 enzyme activity was shown in treatment non-resistant compared to treatment resistant SCZ patients, who essentially present response to the therapy with atypical clozapine but not with typical antipsychotics. Using C. elegans as a model, we tested the consequence of nud genes suppression in the effects of typical and atypical antipsychotics. To assess the role of nud genes and antipsychotic drugs over C. elegans behavior, we measured body bend frequency, egg laying and pharyngeal pumping, which traits are controlled by specific neurons and neurotransmitters known to be involved in SCZ, as dopamine and serotonin. Evaluation of metabolic and behavioral response to the pharmacotherapy with these antipsychotics demonstrates an important unbalance in serotonin pathway in both nud-1 and nud-2 knockout worms, with more significant effects for nud-2 knockout. The present data also show an interesting trend of mutant knockout worm strains to present a metabolic profile closer to that observed for the wild-type animals after the treatment with the typical antipsychotic haloperidol, but which was not observed for the treatment with the atypical antipsychotic clozapine. Paradoxically, behavioral assays showed more evident effects for clozapine than for haloperidol, which is in line with previous studies with rodent animal models and clinical evaluations with SCZ patients. In addition, the validity and reliability of using this experimental animal model to further explore the convergence between the dopamine/serotonin pathways and neurodevelopmental processes was demonstrated here, and the potential usefulness of this model for evaluating the metabolic consequences of treatments with antipsychotics is also suggested.

Topics: Animals; Animals, Genetically Modified; Antipsychotic Agents; Behavior, Animal; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Carrier Proteins; Clozapine; Disease Models, Animal; Haloperidol; Movement; Neurotransmitter Agents; Pharynx; Proton Magnetic Resonance Spectroscopy; Reproducibility of Results; Reproduction; Schizophrenia; Serotonin

We previously reported that centrally acting non-narcotic antitussives, including tipepidine, inhibit G-protein-coupled inwardly rectifying potassium (GIRK) channel-activated currents of neurons. In addition, when administered at a cough suppressant dose, the drugs ameliorated the symptoms of various models of intractable brain disease in rodents. In the current study, we investigated whether tipepidine causes recovery from schizophrenia-like cognitive dysfunction, which was induced by MK-801 (0.2 mg/kg, i.p.) in mice. We also examined the effect of tipepidine and clozapine co-administration on the dysfunction. Moreover, we studied whether clozapine inhibits GIRK channel activated currents in single brain neurons using the patch-clamp technique. Tipepidine elicited recovery from MK-801-induced cognitive impairment in the novel objective recognition test and Y-maze test. Further, co-administration of tipepidine and clozapine, at subthreshold doses of each drug, improved MK-801-induced cognitive impairment in the novel objective recognition test. Clozapine (3 × 10

Topics: Animals; Antidepressive Agents; Antitussive Agents; Clozapine; Cognitive Dysfunction; Disease Models, Animal; Dizocilpine Maleate; Dopaminergic Neurons; G Protein-Coupled Inwardly-Rectifying Potassium Channels; Male; Mice; Patch-Clamp Techniques; Piperidines; Rats; Rats, Wistar; Schizophrenia; Ventral Tegmental Area

Cuprizone (CPZ), a copper chelator that has been shown to selectively damage white matter, can induce a novel animal model to mimic some symptoms of schizophrenia. This study aimed to examine the effect of clozapine (CLZ) on behavioural changes induced by CPZ exposure and try to explore the underlying mechanisms. Behavioural abnormalities associated with feeding mice a 0.4% (w/w) CPZ-containing diet were assessed by Y-maze, spontaneous locomotor activity, and climbing tests. CLZ treatment reversed the increase in total explored distance, exploring velocity, locomotor movements, climbing behaviours and glial activation induced by CPZ exposure. Our findings indicate that increased glial activation may be related to behavioural abnormalities in CPZ exposure mice and that anti-inflammatory properties may be involved in the CLZ mechanisms. CPZ short-term exposure with a higher dosage may offer a useful model to study some aspects of schizophrenia and evaluate the efficacy of antipsychotics.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Cuprizone; Disease Models, Animal; Male; Mice; Mice, Inbred C57BL; Neuroglia; Schizophrenia

Methylazoxymethanol (MAM)-treated pregnant rat at gestation day (GD) 17 has been shown to be a valuable developmental animal model for schizophrenia. Yet, this model remains to be established in mice. In the present study, we examined behavioral, cytoarchitectural, and neurochemical changes in the offspring of MAM-treated mice and validated the model's face, construct and predictive validities. We found that in contrast to a single injection of MAM to dams at GD 15, 16 or 17, its daily administration from GD 15 to 17 led to deficits in prepulse inhibition (PPI) of startle in the post-pubertal offspring. In addition, we observed behavioral deficits in working memory and social interactions, as well as an increase in locomotor activity induced by the NMDA antagonist MK-801 in GD15-17 MAM offspring. These animals also showed a reduction in the volume of the prefrontal cortex (PFC) and hippocampus, neuroanatomical changes such as discontinuities and heterotopias in the hippocampus, and an increase of DA level and DOPAC/DA ratio in the medial PFC. Atypical antipsychotic drugs clozapine, risperidone, and aripiprazole, but not the typical drug haloperidol, reversed the deficit in PPI and social withdrawal in the offspring of MAM-treated dams. In contrast, MK-801-induced hyperactivity in MAM mice was reversed by both and typical or atypical antipsychotic drugs. Taken together, the treatment of pregnant mice with MAM during GD 15-17 offers a new approach to study neurobiological mechanisms involved in the pathogenesis of schizophrenia.

Topics: Animals; Antipsychotic Agents; Aripiprazole; Behavior, Animal; Clozapine; Disease Models, Animal; Female; Haloperidol; Hippocampus; Methylazoxymethanol Acetate; Mice; Motor Activity; Pregnancy; Prenatal Exposure Delayed Effects; Prepulse Inhibition; Risperidone; Schizophrenia

The atypical antipsychotic agent, clozapine, is used to treat a variety of neurological disorders including schizophrenia and Parkinson's disease and readily crosses the blood brain barrier to interact with a wide range of neuroreceptors including those for dopamine and serotonin. Recent work has shown that clozapine can reduce neuroinflammation in experimental autoimmune encephalomyelitis, a neuroinflammatory model of multiple sclerosis (MS) and mediates its effects in the central nervous system. To further characterise the protection provided by clozapine, the cuprizone model of demyelination was used to assess the effect of clozapine treatment on the cellular events surrounding demyelination and remyelination. Using this model of non-immune demyelination, we found that clozapine administration was unable to prevent demyelination, but when administered post demyelination, was able to enhance the rate of functional recovery. The more rapid improvement of clozapine-treated mice correlated with a decreased level of astrocyte and microglial activation but only modestly enhanced remyelination. Together, these studies highlight the potential of clozapine to support enhanced functional recovery after demyelination, such as that occurring during MS.

Topics: Animals; Astrocytes; Central Nervous System; Clozapine; Cuprizone; Demyelinating Diseases; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental; Female; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Myelin Sheath

Antipsychotic drugs haloperidol and clozapine have been reported to increase the sensitivity of retinal ganglion cells (RGCs) to flashes of light in the P23H rat model of retinitis pigmentosa. In order to better understand the effects of these antipsychotic drugs on the visual responses of P23H rat RGCs, I examined the responses of RGCs to a drifting sinusoidal grating of various contrasts. In-vitro multielectrode array recordings were made from P23H rat RGCs and healthy Sprague-Dawley (SD) rat RGCs. Retinas were stimulated with a drifting sinusoidal grating with eight values of contrast (0, 4, 6, 8.5, 13, 26, 51, and 83%). Contrast response functions based on response amplitudes were fitted with a hyperbolic ratio function and contrast thresholds were determined from the fitted curves. SD rat RGCs were divided into two categories, saturating and non-saturating cells, based on whether they showed saturation of responses at high contrast levels. Most SD rat RGCs (58%) were saturating cells. Haloperidol and clozapine decreased the responses of saturating SD rat RGCs to all grating contrasts, except for the highest contrast tested. Clozapine also decreased the responses of non-saturating SD rat RGCs to all grating contrasts, except for the highest contrast tested. Haloperidol did not however significantly affect the responses of non-saturating SD rat RGCs. Haloperidol and clozapine increased the contrast thresholds of both saturating and non-saturating cells in SD rat retinas. Most (73%) P23H rat RGCs could be categorized as either saturating or non-saturating cells. The remaining 'uncategorized' cells were poorly responsive to the drifting grating and were analyzed separately. Haloperidol and clozapine increased the responses of non-saturating and uncategorized P23H rat RGCs to most grating contrasts, including the highest contrast tested. Haloperidol and clozapine also increased the responses of saturating P23H rat RGCs to most grating contrasts but these increases were not statistically significant. Haloperidol and clozapine decreased the contrast thresholds of saturating cells, non-saturating cells and uncategorized cells in P23H rat retinas, although the decrease in contrast thresholds of saturating cells was not found to be statistically significant. Overall, the findings show that haloperidol and clozapine have differential effects on the contrast response functions of SD and P23H rat RGCs. In contrast to the effects observed on SD rat RGCs, both halo

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Haloperidol; Male; Photic Stimulation; Rats; Rats, Sprague-Dawley; Retina; Retinal Ganglion Cells; Retinitis Pigmentosa

Chronic social stress and/or pharmacological treatments differentially modulate the expression of c-Fos, a marker of neuronal activity, in subregions of the rat brain. Here, we examined the effect of the atypical antipsychotic Clozapine (Clz) (20 mg/kg/day for 3 weeks) on the neuronal activation pattern of c-Fos protein expression in stress-relevant brain subregions of adult male Wistar rats exposed to chronic social isolation (CSIS: 3 weeks), an animal model of depression and schizophrenia, and controls. The protein expression of c-Fos was also used to map neuronal populations in brain subregions activated by CSIS alone. Subregions which showed significantly increased c-Fos protein expression following CSIS included the retrosplenial cortex (RSC), (subregions:RSC granular cortex, c region (RSGc) and dysgranular (RSD)), dentate gyrus, dorsal (DGd), paraventricular thalamic nucleus, posterior part (PVP), lateral (LA)/basolateral (BL) complex of amygdala, caudate putamen (CPu) and accumbens nucleus, shell (AcbSh). Increases in c-Fos protein expression in the RSGc, RSD, DGd, PVP, LA/BL complex of amygdala and striatum (CPu, Acb Core (AcbC) and AcbSh) following Clz treatment in controls were found. Clz applied simultaneously with CSIS modulated neuronal activity in CPu, AcbC and AcbSh subregions compared to CSIS alone, increasing c-Fos protein expression. Furthermore, Clz revealed synergistic effects with CSIS in the CA1d and PVP. These identified neural circuits reflect brain subregions activated following CSIS and/or Clz administration. These data further contribute to the understanding of the effectiveness of Clz in the modulation of brain subregion activation in response to CSIS.

Topics: Animals; Antipsychotic Agents; Brain; Clozapine; Corpus Striatum; Depression; Disease Models, Animal; Gyrus Cinguli; Male; Neostriatum; Neurons; Nucleus Accumbens; Proto-Oncogene Proteins c-fos; Rats; Rats, Wistar; Schizophrenia; Social Isolation; Stress, Psychological

Asenapine maleate (AM) is an atypical antipsychotic that, unlike many other antipsychotics, shows some efficacy in treating cognitive dysfunction in schizophrenia. Normal cognitive function has long since been associated with high frequency neuronal oscillations. However, recent research has highlighted the potential importance of low frequency oscillations. Here, the impact of AM on low frequency neural oscillatory activity was evaluated in the methylazoxymethanol acetate (MAM) rat model system used for the study schizophrenia, and the oscillatory signatures compared to those of haloperidol (HAL) and clozapine (CLZ). AM and CLZ normalized low frequency spectral power deficits in the prefrontal cortex, while HAL and AM reversed corticostriatal and corticocortical delta coherence deficits. However, only chronic AM administration normalized corticostriatal and corticocortical delta coherence deficits between 3-4 Hz. These findings support the idea that antipsychotic-induced amelioration of both delta coherence and power may be important for therapeutic efficacy in treating the cognitive deficits inherent in schizophrenia.

Topics: Animals; Antipsychotic Agents; Brain; Clozapine; Delta Rhythm; Dibenzocycloheptenes; Disease Models, Animal; Haloperidol; Heterocyclic Compounds, 4 or More Rings; Rats; Rats, Sprague-Dawley; Schizophrenia

The methionine-folate cycle-dependent one-carbon metabolism is implicated in the pathophysiology of schizophrenia. Since schizophrenia is a developmental disorder, we examined the effects that perturbation of the one-carbon metabolism during gestation has on mice progeny. Pregnant mice were administered methionine equivalent to double their daily intake during the last week of gestation. Their progeny (MET mice) exhibited schizophrenia-like social deficits, cognitive impairments and elevated stereotypy, decreased neurogenesis and synaptic plasticity, and abnormally reduced local excitatory synaptic connections in CA1 neurons. Neural transcript expression of only one gene, encoding the Npas4 transcription factor, was >twofold altered (downregulated) in MET mice; strikingly, similar Npas4 downregulation occurred in the prefrontal cortex of human patients with schizophrenia. Finally, therapeutic actions of typical (haloperidol) and atypical (clozapine) antipsychotics in MET mice mimicked effects in human schizophrenia patients. Our data support the validity of MET mice as a model for schizophrenia, and uncover methionine metabolism as a potential preventive and/or therapeutic target.

Topics: Animals; Antipsychotic Agents; Basic Helix-Loop-Helix Transcription Factors; CA1 Region, Hippocampal; Clozapine; Developmental Disabilities; Disease Models, Animal; Female; Folic Acid; Haloperidol; Humans; Male; Methionine; Mice; Neurogenesis; Neuronal Plasticity; One-Carbon Group Transferases; Prefrontal Cortex; Pregnancy; Prenatal Exposure Delayed Effects; Schizophrenia; Stereotyped Behavior; Tetrahydrofolates

Schizophrenia is a severe syndrome that affects about 1% of the world population. Since the mid-1950s, antipsychotics have been used to treat schizophrenia with preference for treating positive symptoms; however, their tolerance level is low, there are numerous side effects, and only some patients respond to the treatment. Antipsychotic medications that are more effective, better tolerated, and with fewer adverse effects are urgently needed. Given the accumulating evidence of the role filled by the ErbB signaling network in the biology of the dopamine, GABA, and glutamate systems, and in the etiology of schizophrenia, we hypothesized that the ErbB network is a candidate for development of a novel agent through which various symptoms of schizophrenia and other psychiatric disorders might be treated. Herein, we studied, in mice, the capability of blocking the ErbB signaling, in comparison with the atypical antipsychotic drug clozapine, to counter schizophrenia-like behavior induced by acute and sub-chronic phencyclidine (PCP), and determined whether inhibition of the ErbB networks induced weight gain and affected social and exploratory behavior, and metabolic syndrome markers. We demonstrated that administration of the pan-ErbB inhibitor JNJ28871063 (JNJ) reduced the level of activity in the open field induced by an acute injection of PCP. Moreover, the ability of JNJ to attenuate the effect of PCP is as effective as clozapine. In addition and like clozapine, JNJ normalized social behavior impairment induced by sub-chronic PCP and stress. Adult JNJ-treated mice displayed normal sociability and exploratory behavior, and their serum cholesterol, LDL, and HDL levels were lower than in the saline-treated mice. Sub-chronic treatment did not affect weight gain, glucose levels, and the activity of hepatic enzymes catalase and SOD. These data suggest that treatment with JNJ attenuates abnormal behaviors induced by PCP, and has similar effects as the antipsychotic drug clozapine, with no adverse effects. Thus, the ErbB signaling can serve as a new starting point for non-dopaminergic-based drug development of schizophrenia.

Topics: Animals; Animals, Outbred Strains; Antipsychotic Agents; Clozapine; Disease Models, Animal; ErbB Receptors; Male; Metabolic Syndrome; Mice, Inbred ICR; Morpholines; Phencyclidine; Protein Kinase Inhibitors; Pyrimidines; Schizophrenia; Schizophrenic Psychology; Signal Transduction

Death by suicide is 5 times higher among schizophrenia patients than in the general population. There is now compelling evidence suggesting that the pathophysiology of suicide in schizophrenia does not involve central serotonergic neurotransmission disturbances, as has been shown in other contexts. We recently developed and characterized a murine Two-Hit Model of Suicide-related behavior in a schizophrenia-like context (THMS) (gestational inflammation with polyI:C at gestational day 12 followed by post-weaning social isolation). In this THMS model, we have recently shown that the atypical antipsychotic clozapine normalized the prepulse inhibition (PPI) deficits as well suicide-related, impulsive aggressive and anxiety-like behaviors. While the mechanisms underlying the suicide-reducing benefits of clozapine in schizophrenic patients are not well understood, previous works have revealed that clozapine alters brain levels of neurosteroids, such as allopregnanolone. In the present study, we thus investigated the role of endogenous neurosteroids in clozapine action by evaluating whether the 5α-reductase inhibitor finasteride could overturn the ability of clozapine to reduce suicide-related behaviors. We found that clozapine significantly improved the PPI deficits in THMS mice, which could not be reversed by finasteride treatment. However, finasteride counteracted the ability of clozapine to decrease the exploratory behaviors in the open-field test. In the resident-intruder test, THMS mice showed exacerbated aggressiveness and impulsivity following finasteride alone. In this resident-intruder paradigm, clozapine alone effectively blocked the finasteride-enhanced effects on aggression and impulsivity. Altogether, these findings support the existence of a complex interaction between clozapine and neurosteroids in THMS mice. Further investigations are now required to clarify the details of the molecular mechanisms involved.

Topics: 5-alpha Reductase Inhibitors; Acoustic Stimulation; Aggression; Animals; Animals, Newborn; Antipsychotic Agents; Clozapine; Disease Models, Animal; Exploratory Behavior; Female; Finasteride; Interpersonal Relations; Male; Mice; Mice, Inbred C57BL; Polydeoxyribonucleotides; Reflex, Startle; Schizophrenia; Schizophrenic Psychology; Suicide

NMDA receptor (NMDAr) hypofunction has been widely used as a schizophrenia model. Decreased activation of NMDAr is associated with a disrupted excitation/inhibition balance in the prefrontal cortex and with alterations in gamma synchronization. Our aim was to investigate whether this phenomenon could be reproduced in the spontaneous oscillatory activity generated by the local prefrontal network in vitro and, if so, to explore the effects of antipsychotics on the resulting activity. Extracellular recordings were obtained from prefrontal cortex slices bathed in in vivo-like ACSF solution. Slow (<1 Hz) oscillations consisting of interspersed Up (active) and Down (silent) states spontaneously emerged. Fast-frequency oscillations (15-90 Hz) occurred during Up states. We explored the effects of the NMDAr antagonist MK-801 on the spontaneously generated activity. Bath-applied MK-801 induced a dose-dependent decrease in Up-state duration and in the frequency of Up states. However, the beta/gamma power during Up states significantly increased; this increase was in turn prevented by the antipsychotic drug clozapine. The increased beta/gamma power with NMDAr blockade implies that NMDAr activation in physiological conditions prevents hypersynchronization in this frequency range. High-frequency hypersynchronization following NMDAr blockade occurring in cortical slices suggests that-at least part of-the underlying mechanisms of this schizophrenia feature persist in the local cortical circuit, even in the absence of long-range cortical or subcortical inputs. The observed action of clozapine decreasing hypersynchronization in the local circuit may be one of the mechanisms of action of clozapine in preventing schizophrenia symptoms derived from NMDA hypofunction.

Topics: Animals; Beta Rhythm; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ferrets; Gamma Rhythm; In Vitro Techniques; Male; Organ Culture Techniques; Prefrontal Cortex; Receptors, N-Methyl-D-Aspartate; Schizophrenia

Oxidative stress and mitochondrial dysfunction have been implicated in the pathophysiology of schizophrenia.. We investigated whether antipsychotic clozapine modulates nicotinamide adenine dinucleotide phosphate oxidase and mitochondrial burdens induced by phencyclidine in mice.. We examined the effect of clozapine on nicotinamide adenine dinucleotide phosphate oxidase activation, mitochondrial burdens (i.e. oxidative stress and mitochondrial dysfunction), and activities of enzymatic antioxidant in the prefrontal cortex, and subsequent abnormal behaviors induced by repeated treatment with phencyclidine. p47. Phencyclidine treatment resulted in an early increase nicotinamide adenine dinucleotide phosphate oxidase activity, membrane translocation of p47

Topics: Animals; Antioxidants; Antipsychotic Agents; Behavior, Animal; Chromones; Clozapine; Disease Models, Animal; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitochondria; Morpholines; NADPH Oxidases; Oxidative Stress; Phencyclidine; Phosphatidylinositol 3-Kinase; Proto-Oncogene Proteins c-akt; Schizophrenia; Signal Transduction

Schizophrenia is a severely debilitating neurodevelopmental disorder. Establishing a causal link between circuit dysfunction and particular behavioral traits that are relevant to schizophrenia is crucial to shed new light on the mechanisms underlying the pathology. We studied an animal model of the human 22q11 deletion syndrome, the mutation that represents the highest genetic risk of developing schizophrenia. We observed a desynchronization of hippocampal neuronal assemblies that resulted from parvalbumin interneuron hypoexcitability. Rescuing parvalbumin interneuron excitability with pharmacological or chemogenetic approaches was sufficient to restore wild-type-like CA1 network dynamics and hippocampal-dependent behavior during adulthood. In conclusion, our data provide insights into the network dysfunction underlying schizophrenia and highlight the use of reverse engineering to restore physiological and behavioral phenotypes in an animal model of neurodevelopmental disorder.

Topics: 22q11 Deletion Syndrome; Action Potentials; Animals; Animals, Newborn; CA1 Region, Hippocampal; Clozapine; Disease Models, Animal; Female; Humans; Male; Mental Disorders; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nerve Net; Neuregulins; Neurons; Nonlinear Dynamics; Parvalbumins; Prepulse Inhibition; Reflex, Startle; Schizophrenia

The bed nucleus of the stria terminalis (BNST) is a brain region important for regulating anxiety-related behavior in both humans and rodents. Here we used a chemogenetic strategy to investigate how engagement of G protein-coupled receptor (GPCR) signaling cascades in genetically defined GABAergic BNST neurons modulates anxiety-related behavior and downstream circuit function. We saw that stimulation of vesicular γ-aminobutyric acid (GABA) transporter (VGAT)-expressing BNST neurons using hM3Dq, but neither hM4Di nor rM3Ds designer receptors exclusively activated by a designer drug (DREADD), promotes anxiety-like behavior. Further, we identified that activation of hM3Dq receptors in BNST VGAT neurons can induce a long-term depression-like state of glutamatergic synaptic transmission, indicating DREADD-induced changes in synaptic plasticity. Further, we used DREADD-assisted metabolic mapping to profile brain-wide network activity following activation of G

Topics: Animals; Anti-Anxiety Agents; Anxiety; Brain Mapping; Cannabinoid Receptor Antagonists; Clozapine; Dark Adaptation; Disease Models, Animal; Estrenes; Excitatory Postsynaptic Potentials; Exploratory Behavior; Green Fluorescent Proteins; GTP-Binding Protein alpha Subunits, Gq-G11; In Vitro Techniques; Male; Maze Learning; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neurons; Phosphodiesterase Inhibitors; Piperazines; Pyrrolidinones; Receptors, Drug; Rimonabant; RNA, Messenger; Septal Nuclei; Serotonin Receptor Agonists; Signal Transduction; Sodium Channel Blockers; Tetrodotoxin; Vesicular Inhibitory Amino Acid Transport Proteins

A series of twenty two (E)-N-cinnamoyl aminoalkanols derivatives monosubstituted in phenyl ring with 4-Cl, 4-CH

Topics: Amino Alcohols; Animals; Anticonvulsants; Crystallography, X-Ray; Disease Models, Animal; Dose-Response Relationship, Drug; Electroshock; Mice; Models, Molecular; Molecular Structure; Rats; Seizures; Structure-Activity Relationship

Chronic psychosocial stress modulates brain antioxidant systems and causes neuroinflammation that plays a role in the pathophysiology of depression. Although the antidepressant fluoxetine (FLX) represents the first-line treatment for depression and the atypical antipsychotic clozapine (CLZ) is considered as a second-line treatment for psychotic disorders, the downstream mechanisms of action of these treatments, beyond serotonergic or dopaminergic signaling, remain elusive. We examined behavioral changes, glutathione (GSH)-dependent defense and levels of proinflammatory mediators in the prefrontal cortex (PFC) of adult male Wistar rats exposed to 21days of chronic social isolation (CSIS). We also tested the ability of FLX (15mg/kg/day) or CLZ (20mg/kg/day), applied during CSIS, to prevent stress-induced changes. CSIS caused depressive- and anxiety-like behaviors, compromised GSH-dependent defense, and induced nuclear factor-kappa B (NF-κB) activation with a concomitant increase in cytosolic levels of proinflammatory mediators cyclooxigenase-2, interleukin-1beta and tumor necrosis factor-alpha in the PFC. NF-κB activation and proinflammatory response in the PFC were not found in CSIS rats treated with FLX or CLZ. In contrast, only FLX preserved GSH content in CSIS rats. CLZ not only failed to protect against CSIS-induced GSH depletion, but it diminished its levels when applied to non-stressed rats. In conclusion, prefrontal cortical GSH depletion and the proinflammatory response underlying depressive- and anxiety-like states induced by CSIS were prevented by FLX. The protective effect of CLZ, which was equally effective as FLX on the behavioral level, was limited to proinflammatory components. Hence, different mechanisms underlie the protective effects of these two drugs in CSIS rats.

Topics: Animals; Antidepressive Agents; Clozapine; Cytokines; Defense Mechanisms; Disease Models, Animal; Fluoxetine; Glutathione; Glutathione Peroxidase; Glutathione Reductase; Male; Mood Disorders; NADP; NF-kappa B; Nitric Oxide Synthase Type II; Prefrontal Cortex; Rats; Rats, Wistar; Social Isolation

Chronic treatment with second-generation antipsychotic drugs (SGAs) has been associated with an increased risk of metabolic syndrome. To evaluate the longitudinal changes in glucose-lipid homeostasis after SGA use, we studied the time-dependent effects of olanzapine (OLZ) (3 mg/kg, b.i.d.) or clozapine (CLZ) (20 mg/kg, b.i.d.) treatment on metabolic profiles for 9 weeks in rats. Although only OLZ significantly increased body weight in rats, both OLZ and CLZ elevated blood lipid levels. Chronic OLZ treatment induced significant weight gain leading to a higher fasting insulin level and impaired glucose tolerance, whereas CLZ lowered fasting insulin levels and impaired glucose tolerance independent of weight gain. Treatment with both drugs deranged AKT/GSK phosphorylation and up-regulated muscarinic M3 receptors in the rats' livers. Consistent with an elevation in lipid levels, both OLZ and CLZ significantly increased the protein levels of nuclear sterol regulatory element-binding proteins (SREBPs) in the liver, which was associated with improvement in hepatic histamine H1R. However, enhanced carbohydrate response element binding protein (ChREBP) signalling was observed in only CLZ-treated rats. These results suggest that SGA-induced glucose-lipid metabolic disturbances could be independent of weight gain, possibly through activation of SREBP/ChREBP in the liver.

Topics: Adipose Tissue, White; Animals; Antipsychotic Agents; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Blood Glucose; Clozapine; Disease Models, Animal; Glucose; Glucose Metabolism Disorders; Humans; Lipid Metabolism; Lipid Metabolism Disorders; Liver; Metabolic Networks and Pathways; Olanzapine; Rats; Sterol Regulatory Element Binding Proteins; Weight Gain

Depression is a prevalent psychiatric disorder with an increasing impact in global public health. However, a large proportion of patients treated with currently available antidepressant drugs fail to achieve remission. Recently, antipsychotic drugs have received approval for the treatment of antidepressant-resistant forms of major depression. The modulation of adult neuroplasticity, namely hippocampal neurogenesis and neuronal remodeling, has been considered to have a key role in the therapeutic effects of antidepressants. However, the impact of antipsychotic drugs on these neuroplastic mechanisms remains largely unexplored. In this study, an unpredictable chronic mild stress protocol was used to induce a depressive-like phenotype in rats. In the last 3 weeks of stress exposure, animals were treated with two different antipsychotics: haloperidol (a classical antipsychotic) and clozapine (an atypical antipsychotic). We demonstrated that clozapine improved both measures of depressive-like behavior (behavior despair and anhedonia), whereas haloperidol aggravated learned helplessness in the forced-swimming test and behavior flexibility in a cognitive task. Importantly, an upregulation of adult neurogenesis and neuronal survival was observed in animals treated with clozapine, whereas haloperidol promoted a downregulation of these processes. Furthermore, clozapine was able to re-establish the stress-induced impairments in neuronal structure and gene expression in the hippocampus and prefrontal cortex. These results demonstrate the modulation of adult neuroplasticity by antipsychotics in an animal model of depression, revealing that the atypical antipsychotic drug clozapine reverts the behavioral effects of chronic stress by improving adult neurogenesis, cell survival and neuronal reorganization.

Topics: Affect; Animals; Antidepressive Agents; Antipsychotic Agents; Behavior, Animal; Cell Survival; Clozapine; Depression; Disease Models, Animal; Haloperidol; Hippocampus; Male; Neurogenesis; Neuronal Plasticity; Prefrontal Cortex; Rats; Rats, Wistar; Swimming

Topics: Animals; Behavior, Animal; Clozapine; Cyclopropanes; Disease Models, Animal; GABAergic Neurons; Gene Knock-In Techniques; Genetic Engineering; Humans; Injections, Spinal; Interneurons; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Pruritus; Receptor, Muscarinic M3; Spinal Cord Dorsal Horn; Treatment Outcome

Inspiratory accessory respiratory muscles (ARMs) enhance ventilation when demands are high, such as during exercise and/or pathological conditions. Despite progressive degeneration of phrenic motor neurons innervating the diaphragm, amyotrophic lateral sclerosis (ALS) patients and rodent models are able to maintain ventilation at early stages of disease. In order to assess the contribution of ARMs to respiratory compensation in ALS, we examined the activity of ARMs and ventilation throughout disease progression in SOD1

Topics: Amyotrophic Lateral Sclerosis; Animals; Antigens, CD; Antigens, Differentiation, Myelomonocytic; Brain Stem; Clozapine; Disease Models, Animal; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Homeodomain Proteins; Humans; Interneurons; Male; Membrane Potentials; Mice; Mice, Transgenic; Plasma Membrane Neurotransmitter Transport Proteins; Receptor, Muscarinic M3; Receptors, Muscarinic; Respiration; Respiratory Muscles; Spinal Cord; Superoxide Dismutase; Transcription Factors

Schizophrenia patients who do not respond to clozapine treatment represent the most debilitating type of schizophrenia with unmet needs for novel interventions. To date there is no validated animal model for clozapine-refractory schizophrenia.. We used poor performance in the social preference (SP) test of C57/BL mice exposed to subchronic phencyclidine (PCP) as a correlate of negative signs of schizophrenia. Subsequently the mice were treated with clozapine and according to their SP they were defined as responding (i.e. clozapine/PCP ratio>1.5 SD) or non-responsive to clozapine. In each generation the responding mice were mated to produce the next generation. Unfortunately, the clozapine- non-responsive mice failed to proliferate and were thus excluded from the analyses. This forward genetic paradigm was used to produce the next generation of clozapine-responding mice. We assessed brain glutamic acid decarboxylase-67 (GAD67) protein levels, as a GABA-ergic marker, in the F2 and F3 generations.. Already in the F1 generation of male mice, but not females, it was possible to discriminate between clozapine-responders and non-responders. The rate of responders within each consecutive generation, increased. The increase was more pronounced in females. Up-regulation of GAD67 levels was detected between F2 and F3 only in male clozapine-responder mice, but not in females.. This preliminary proof-of-concept study succeeded in producing a trans-generation enrichment of clozapine-responsiveness trait in a hypo-glutamatergic animal model of negative signs of schizophrenia. This model may serve as a platform to better characterize the clozapine responsiveness trait and offer a model for clozapine-responsive schizophrenia.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Female; Frontal Lobe; Glutamate Decarboxylase; Glutamic Acid; Hippocampus; Male; Mice; Mice, Inbred C57BL; Phencyclidine; Schizophrenia; Selective Breeding; Social Behavior

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep. OSA leads to high cardiovascular morbidity and mortality. The pathogenesis of OSA has been linked to a defect in neuromuscular control of the pharynx. There is no effective pharmacotherapy for OSA. The objective of this study was to determine whether upper airway patency can be improved using chemogenetic approach by deploying designer receptors exclusively activated by designer drug (DREADD) in the hypoglossal motorneurons. DREADD (rAAV5-hSyn-hM3(Gq)-mCherry) and control virus (rAAV5-hSyn-EGFP) were stereotactically administered to the hypoglossal nucleus of C57BL/6J mice. In 6-8 weeks genioglossus EMG and dynamic MRI of the upper airway were performed before and after administration of the DREADD ligand clozapine-N-oxide (CNO) or vehicle (saline). In DREADD-treated mice, CNO activated the genioglossus muscle and markedly dilated the pharynx, whereas saline had no effect. Control virus treated mice showed no effect of CNO. Our results suggest that chemogenetic approach can be considered as a treatment option for OSA and other motorneuron disorders.

Topics: Animals; Antipsychotic Agents; Clozapine; Dependovirus; Disease Models, Animal; Electromyography; Genes, Reporter; Genetic Vectors; Green Fluorescent Proteins; Hypoglossal Nerve; Injections, Intraventricular; Luminescent Proteins; Magnetic Resonance Imaging; Male; Mice; Mice, Inbred C57BL; Neurons; Pharynx; Red Fluorescent Protein; Sleep Apnea, Obstructive; Stereotaxic Techniques

Previous studies on the N-phenylpiperazine derivative LASSBio-579 have suggested that LASSBio-579 has an atypical antipsychotic profile. It binds to D2, D4 and 5-HT1A receptors and is effective in animal models of schizophrenia symptoms (prepulse inhibition disruption, apomorphine-induced climbing and amphetamine-induced stereotypy). In the current study, we evaluated the effect of LASSBio-579, clozapine (atypical antipsychotic) and haloperidol (typical antipsychotic) in the novel object recognition task, a recognition memory model with translational value. Haloperidol (0.01 mg/kg, orally) impaired the ability of the animals (CF1 mice) to recognize the novel object on short-term and long-term memory tasks, whereas LASSBio-579 (5 mg/kg, orally) and clozapine (1 mg/kg, orally) did not. In another set of experiments, animals previously treated with ketamine (10 mg/kg, intraperitoneally) or vehicle (saline 1 ml/100 g, intraperitoneally) received LASSBio-579, clozapine or haloperidol at different time-points: 1 h before training (encoding/consolidation); immediately after training (consolidation); or 1 h before long-term memory testing (retrieval). LASSBio-579 and clozapine protected against the long-term memory impairment induced by ketamine when administered at the stages of encoding, consolidation and retrieval of memory. These findings point to the potential of LASSBio-579 for treating cognitive symptoms of schizophrenia and other disorders.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Haloperidol; Ketamine; Male; Memory, Long-Term; Memory, Short-Term; Mice; Piperazines; Recognition, Psychology; Schizophrenia; Time Factors

We have recently reported that mice born from dams stressed during pregnancy (PRS mice), in adulthood, have behavioral deficits reminiscent of behaviors observed in schizophrenia (SZ) and bipolar (BP) disorder patients. Furthermore, we have shown that the frontal cortex (FC) and hippocampus of adult PRS mice, like that of postmortem chronic SZ patients, are characterized by increases in DNA-methyltransferase 1 (DNMT1), ten-eleven methylcytosine dioxygenase 1 (TET1) and exhibit an enrichment of 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC) at neocortical GABAergic and glutamatergic gene promoters. Here, we show that the behavioral deficits and the increased 5MC and 5HMC at glutamic acid decarboxylase 67 (Gad1), reelin (Reln) and brain-derived neurotrophic factor (Bdnf) promoters and the reduced expression of the messenger RNAs (mRNAs) and proteins corresponding to these genes in FC of adult PRS mice is reversed by treatment with clozapine (5 mg kg(-1) twice a day for 5 days) but not by haloperidol (1 mg kg(-1) twice a day for 5 days). Interestingly, clozapine had no effect on either the behavior, promoter methylation or the expression of these mRNAs and proteins when administered to offspring of nonstressed pregnant mice. Clozapine, but not haloperidol, reduced the elevated levels of DNMT1 and TET1, as well as the elevated levels of DNMT1 binding to Gad1, Reln and Bdnf promoters in PRS mice suggesting that clozapine, unlike haloperidol, may limit DNA methylation by interfering with DNA methylation dynamics. We conclude that the PRS mouse model may be useful preclinically in screening for the potential efficacy of antipsychotic drugs acting on altered epigenetic mechanisms. Furthermore, PRS mice may be invaluable for understanding the etiopathogenesis of SZ and BP disorder and for predicting treatment responses at early stages of the illness allowing for early detection and remedial intervention.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Blotting, Western; Brain; Chromatin Assembly and Disassembly; Clozapine; Disease Models, Animal; Epigenesis, Genetic; Female; Mice; Pregnancy; Prenatal Exposure Delayed Effects; Real-Time Polymerase Chain Reaction; Reelin Protein; Stress, Psychological

Aberrant neural hyperactivity has been observed in early stages of Alzheimer's disease (AD) and may be a driving force in the progression of amyloid pathology. Evidence for this includes the findings that neural activity may modulate β-amyloid (Aβ) peptide secretion and experimental stimulation of neural activity can increase amyloid deposition. However, whether long-term attenuation of neural activity prevents the buildup of amyloid plaques and associated neural pathologies remains unknown. Using viral-mediated delivery of designer receptors exclusively activated by designer drugs (DREADDs), we show in two AD-like mouse models that chronic intermittent increases or reductions of activity have opposite effects on Aβ deposition. Neural activity reduction markedly decreases Aβ aggregation in regions containing axons or dendrites of DREADD-expressing neurons, suggesting the involvement of synaptic and nonsynaptic Aβ release mechanisms. Importantly, activity attenuation is associated with a reduction in axonal dystrophy and synaptic loss around amyloid plaques. Thus, modulation of neural activity could constitute a potential therapeutic strategy for ameliorating amyloid-induced pathology in AD.. A novel chemogenetic approach to upregulate and downregulate neuronal activity in Alzheimer's disease (AD) mice was implemented. This led to the first demonstration that chronic intermittent attenuation of neuronal activity in vivo significantly reduces amyloid deposition. The study also demonstrates that modulation of β-amyloid (Aβ) release can occur at both axonal and dendritic fields, suggesting the involvement of synaptic and nonsynaptic Aβ release mechanisms. Activity reductions also led to attenuation of the synaptic pathology associated with amyloid plaques. Therefore, chronic attenuation of neuronal activity could constitute a novel therapeutic approach for AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Calcium-Binding Proteins; Clozapine; Designer Drugs; Disease Models, Animal; Humans; Insulysin; Lysosomal Membrane Proteins; Male; Mice; Mice, Transgenic; Microfilament Proteins; Nerve Tissue Proteins; Neurotoxicity Syndromes; Presenilin-1; Proto-Oncogene Proteins c-fos; Styrenes; Transduction, Genetic

Schizophrenia patients show a high rate of premature mortality due to suicide. The pathophysiological mechanisms of these suicidal behaviors in schizophrenia do not appear to involve serotonergic neurotransmission as found in the general population. Our aim was to develop an in vivo model of schizophrenia presenting suicide-trait-related behaviors such as aggressiveness, impulsivity, anxiety and helplessness. We opted for a two-hit model: C57BL/6 dams were injected with polyI:C on gestational day 12. The pups were submitted to social isolation for 4weeks after weaning. During the last week of social isolation and 30min before behavioral testing, the mice received vehicle, lithium chloride or clozapine. Lithium chloride is well known for its suicide preventive effects in the non-schizophrenic population, while clozapine is the antipsychotic with the best-established suicide preventive effect. The two-hit model induced several schizophrenia-related and suicide-trait-related behaviors in male, but not female, mice. Additionally, lithium chloride improved prepulse inhibition, aggressiveness, impulsivity and anxiety-like behavior in socially isolated mice only, whereas clozapine prevented behavioral abnormalities mainly in mice prenatally exposed to polyI:C and submitted to isolated rearing. The distinct effects of lithium chloride and clozapine suggested that mice prenatally exposed to polyI:C and submitted to social isolation presented a distinct phenotype from that of mice submitted to social isolation only. Because diagnosing suicidal risk in patients is a challenge for psychiatrists given the lack of specific clinical predictors, our in vivo model could help in gaining a better understanding of the mechanisms underlying suicidal behavior in the context of schizophrenia.

Topics: Aggression; Animals; Antipsychotic Agents; Anxiety; Clozapine; Disease Models, Animal; Female; Lithium Chloride; Mice; Mice, Inbred C57BL; Phenotype; Schizophrenia; Schizophrenic Psychology; Social Isolation; Suicidal Ideation; Suicide Prevention

Receptors for antipsychotics in the hypothalamus contribute to antipsychotics-induced weight gain; however, many of these receptors are also expressed in the intestine. The role of these intestinally-expressed receptors, and their potential modulation of nutrient absorption, have not been investigated in the context of antipsychotics-induced weight gain. Here we tested the effect of dietary fructose and intestinal fructose uptake on clozapine-induced weight gain in mice. Weight gain was determined in wild type mice and mice lacking the GLUT5 fructose transporter that were "orally-administered" 20mg/kg clozapine for 28 days. To assess the role of dietary fructose, clozapine-treated mice were fed controlled diets with different levels of fructose. Effect of clozapine treatment on intestinal fructose transport activity and expression levels of various receptors that bind clozapine, as well as several genes involved in gluconeogenesis and lipogenesis were measured using real-time RT-PCR and western blotting. Oral administration of clozapine significantly increased body weight in wild type C57BL/6 mice but not in GLUT5 null mice. The clozapine-induced weight gain was proportional to the percentage of fructose in the diet. Clozapine-treated mice increased intestinal fructose uptake without changing the intestinal expression level of GLUT5. Clozapine-treated mice expressed significantly higher levels of intestinal H1 histamine receptor in the wild type but not GLUT5 null mice. Clozapine also increased the intestinal expression of fructokinase and several genes involved in gluconeogenesis and lipogenesis. Our results suggest that increased intestinal absorption and metabolism of fructose contributes to clozapine-induced weight gain. Eliminating dietary fructose might prevent antipsychotics-induced weight gain.

Topics: Animals; Antipsychotic Agents; Clozapine; Dietary Carbohydrates; Disease Models, Animal; Fructokinases; Fructose; Glucose Transport Proteins, Facilitative; Glucose Transporter Type 5; Intestinal Absorption; Mice; Mice, Inbred C57BL; Mice, Knockout; Weight Gain

Recent heuristic models of schizophrenia propose that abnormalities in the gamma frequency cerebral oscillations may be closely tied to the pathophysiology of the disorder, with hypofunction of N-methyl-d-aspartate receptors (NMDAr) implicated as having a crucial role. Prepulse inhibition (PPI) is a behavioural measure of sensorimotor gating that is disrupted in schizophrenia. We tested the ability for antipsychotic drugs with diverse pharmacological actions to (1) ameliorate NMDAr antagonist-induced disruptions to gamma oscillations and (2) attenuate NMDAr antagonist-induced disruptions to PPI. We hypothesized that antipsychotic-mediated improvement of PPI deficits would be accompanied by a normalization of gamma oscillatory activity. Wistar rats were implanted with extradural electrodes to facilitate recording of electroencephalogram during PPI behavioural testing. In each session, the rats were administered haloperidol (0.25 mg kg(-1)), clozapine (5 mg kg(-1)), olanzapine (5 mg kg(-1)), LY379268 (3 mg kg(-1)), NFPS (sarcosine, 1 mg kg(-1)), d-serine (1800 mg kg(-1)) or vehicle, followed by the NMDAr antagonists MK-801(0.16 mg kg(-1)), ketamine (5 mg kg(-1)) or vehicle. Outcome measures were auditory-evoked, as well as ongoing, gamma oscillations and PPI. Although treatment with all the clinically validated antipsychotic drugs reduced ongoing gamma oscillations, clozapine was the only compound that prevented the sensory-evoked gamma deficit produced by ketamine and MK-801. In addition, clozapine was also the only antipsychotic that attenuated the disruption to PPI produced by the NMDAr antagonists. We conclude that disruptions to evoked, but not ongoing, gamma oscillations caused by NMDAr antagonists are functionally relevant, and suggest that compounds, which restore sensory-evoked gamma oscillations may improve sensory processing in patients with schizophrenia.

Topics: Amino Acids; Animals; Antipsychotic Agents; Benzodiazepines; Bridged Bicyclo Compounds, Heterocyclic; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Electroencephalography; Haloperidol; Ketamine; Male; Olanzapine; Prepulse Inhibition; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Reflex, Startle; Schizophrenia

Asenapine is an atypical antipsychotic that is currently available for the treatment of schizophrenia and bipolar I disorder. Although the atypical antipsychotics clozapine and olanzapine are effective for depression and anxiety in schizophrenia, as demonstrated by animal model studies, this has not been clarified for asenapine. Therefore, we compared the effects of asenapine in the conditioned fear stress model with those of clozapine and olanzapine.. Rats were individually fear conditioned using electrical foot shock in a Skinner box. Approximately 24 h later, individual animals were returned to the same Skinner box (without electrical shock) and their freezing behaviour was observed for 5 min. Animals were treated with asenapine, clozapine, olanzapine, the 5-HT1A receptor partial agonist buspirone, or the 5-HT2C receptor antagonist SB242084 at 30 min before freezing behaviour assessment. The 5-HT1A receptor antagonist WAY100635 or the 5-HT2C receptor agonist Ro60-0175 was also used concomitantly with asenapine. The effects of asenapine, clozapine, and olanzapine on serotonin release in the rat hippocampus were also measured using in vivo microdialysis.. Asenapine reduced freezing behaviour, while neither clozapine nor olanzapine reduced freezing behaviour. Buspirone and SB242084 also reduced freezing behaviour. The effect of asenapine in reducing freezing behaviour was not altered by the concomitant administration of WAY100635 or Ro60-0175. Both asenapine and clozapine, but not olanzapine, increased serotonin release in the rat hippocampus.. Asenapine may have superior therapeutic effect on anxiety symptoms than other agents, although the underlying mechanism of its anxiolytic activity remains unknown.

Topics: Aminopyridines; Animals; Anti-Anxiety Agents; Antipsychotic Agents; Anxiety; Benzodiazepines; Buspirone; Clozapine; Conditioning, Classical; Dibenzocycloheptenes; Disease Models, Animal; Dose-Response Relationship, Drug; Electroshock; Fear; Heterocyclic Compounds, 4 or More Rings; Hippocampus; Indoles; Male; Olanzapine; Rats; Rats, Sprague-Dawley; Serotonin; Serotonin Antagonists; Serotonin Receptor Agonists; Stress, Psychological

Transplantation of human pluripotent stem cell (hPSC)-derived neurons is a promising avenue for treating disorders including Parkinson's disease (PD). Precise control over engrafted cell activity is highly desired, as cells do not always integrate properly into host circuitry and can cause suboptimal graft function or undesired outcomes. Here, we show tunable rescue of motor function in a mouse model of PD, following transplantation of human midbrain dopaminergic (mDA) neurons differentiated from hPSCs engineered to express DREADDs (designer receptors exclusively activated by designer drug). Administering clozapine-N-oxide (CNO) enabled precise DREADD-dependent stimulation or inhibition of engrafted neurons, revealing D1 receptor-dependent regulation of host neuronal circuitry by engrafted cells. Transplanted cells rescued motor defects, which could be reversed or enhanced by CNO-based control of graft function, and activating engrafted cells drives behavioral changes in transplanted mice. These results highlight the ability to exogenously and noninvasively control and refine therapeutic outcomes following cell transplantation.

Topics: Animals; Cell Differentiation; Cell Line; Clozapine; Disease Models, Animal; Dopaminergic Neurons; Drug Design; Excitatory Postsynaptic Potentials; gamma-Aminobutyric Acid; Glutamates; Human Embryonic Stem Cells; Humans; Mesencephalon; Mice; Motor Activity; Neostriatum; Neurons; Parkinson Disease; Pluripotent Stem Cells; Receptors, Dopamine D1; Stem Cell Transplantation

Temporal lobe epilepsy is the most common form of medically-intractable epilepsy. While seizures in TLE originate in structures such as hippocampus, amygdala, and temporal cortex, they propagate through a crucial relay: the midline/intralaminar thalamus. Prior studies have shown that pharmacological inhibition of midline thalamus attenuates limbic seizures. Here, we examined a recently developed technology, Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), as a means of chemogenetic silencing to attenuate limbic seizures. Adult, male rats were electrically kindled from the amygdala, and injected with virus coding for inhibitory (hM4Di) DREADDs into the midline/intralaminar thalamus. When treated with the otherwise inert ligand Clozapine-N-Oxide (CNO) at doses of 2.5, 5, and 10mg/kg, electrographic and behavioral seizure manifestations were suppressed in comparison to vehicle. At higher doses, we found complete blockade of seizure activity in a subset of subjects. CNO displayed a sharp time-response profile, with significant seizure attenuation seen 20-30min post injection, in comparison to 10 and 40min post injection. Seizures in animals injected with a control vector (i.e., no DREADD) were unaffected by CNO administration. These data underscore the crucial role of the midline/intralaminar thalamus in the propagation of seizures, specifically in the amygdala kindling model, and provide validation of chemogenetic silencing of limbic seizures.

Topics: Amygdala; Analysis of Variance; Animals; Anticonvulsants; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Electric Stimulation; Evoked Potentials; Intralaminar Thalamic Nuclei; Kindling, Neurologic; Male; Maze Learning; Midline Thalamic Nuclei; Rats; Rats, Sprague-Dawley; Seizures

Spatially targeted, genetically-specific strategies for sustained inhibition of nociceptors may help transform pain science and clinical management. Previous optogenetic strategies to inhibit pain have required constant illumination, and chemogenetic approaches in the periphery have not been shown to inhibit pain. Here, we show that the step-function inhibitory channelrhodopsin, SwiChR, can be used to persistently inhibit pain for long periods of time through infrequent transdermally delivered light pulses, reducing required light exposure by >98% and resolving a long-standing limitation in optogenetic inhibition. We demonstrate that the viral expression of the hM4D receptor in small-diameter primary afferent nociceptor enables chemogenetic inhibition of mechanical and thermal nociception thresholds. Finally, we develop optoPAIN, an optogenetic platform to non-invasively assess changes in pain sensitivity, and use this technique to examine pharmacological and chemogenetic inhibition of pain.

Topics: Animals; Cells, Cultured; Channelrhodopsins; Clozapine; Combined Modality Therapy; Disease Models, Animal; Low-Level Light Therapy; Mice; Nociception; Optogenetics; Pain

Topics: Acetylcholine; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Clozapine; Conditioning, Psychological; Disease Models, Animal; Fear; Glutamate Decarboxylase; Hippocampus; Interneurons; Memory Disorders; Mice; Mice, Transgenic; Neuroanatomical Tract-Tracing Techniques; Neuronal Plasticity; Somatostatin; Synapses

In the P23H rat model of retinitis pigmentosa, the dopamine D2 receptor antagonists sulpiride and eticlopride appear to improve visual responses of retinal ganglion cells (RGCs) by increasing light sensitivity of RGCs and transforming abnormal, long-latency ON-center RGCs into OFF-center cells. Antipsychotic drugs are believed to mediate their therapeutic benefits by blocking D2 receptors. This investigation was conducted to test whether haloperidol (a typical antipsychotic drug) and clozapine (an atypical antipsychotic drug) could similarly alter the light responses of RGCs in the P23H rat retina.. Extracellular recordings were made from RGCs in isolated P23H rat retinas. Responses of RGCs to flashes of light were evaluated before and during bath application of a drug.. Both haloperidol and clozapine increased light sensitivity of RGCs on average by ∼0.3 log unit. For those ON-center RGCs that exhibit an abnormally long-latency response to the onset of a small spot of light, both haloperidol and clozapine brought out a short-latency OFF response and markedly reduced the long-latency ON response. The selective serotonin 5-HT2A antagonist MDL 100907 had similar effects on RGCs.. The effects of haloperidol on light responses of RGCs can be explained by its D2 receptor antagonism. The effects of clozapine on light responses of RGCs on the other hand may largely be due to its 5-HT2A receptor antagonism. Overall, the results suggest that antipsychotic drugs may be useful in improving vision in patients with retinitis pigmentosa.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Haloperidol; Rats; Retinal Ganglion Cells; Retinitis Pigmentosa

Exercise alleviates pain and it is a central component of treatment strategy for chronic pain in clinical setting. However, little is known about mechanism of this exercise-induced hypoalgesia. The mesolimbic dopaminergic network plays a role in positive emotions to rewards including motivation and pleasure. Pain negatively modulates these emotions, but appropriate exercise is considered to activate the dopaminergic network. We investigated possible involvement of this network as a mechanism of exercise-induced hypoalgesia.. In the present study, we developed a protocol of treadmill exercise, which was able to recover pain threshold under partial sciatic nerve ligation in mice, and investigated involvement of the dopaminergic reward network in exercise-induced hypoalgesia. To temporally suppress a neural activation during exercise, a genetically modified inhibitory G-protein-coupled receptor, hM4Di, was specifically expressed on dopaminergic pathway from the ventral tegmental area to the nucleus accumbens.. The chemogenetic-specific neural suppression by Gi-DREADD system dramatically offset the effect of exercise-induced hypoalgesia in transgenic mice with hM4Di expressed on the ventral tegmental area dopamine neurons. Additionally, anti-exercise-induced hypoalgesia effect was significantly observed under the suppression of neurons projecting out of the ventral tegmental area to the nucleus accumbens as well.. Our findings suggest that the dopaminergic pathway from the ventral tegmental area to the nucleus accumbens is involved in the anti-nociception under low-intensity exercise under a neuropathic pain-like state.

Topics: Animals; Clozapine; Disease Models, Animal; Dopamine; Dopamine Plasma Membrane Transport Proteins; Exercise Test; Exercise Therapy; Hyperalgesia; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neuralgia; Nucleus Accumbens; Pain Measurement; Pain Threshold; Phosphopyruvate Hydratase; Receptors, G-Protein-Coupled; Serotonin Antagonists; Tyrosine 3-Monooxygenase; Ventral Tegmental Area

Previously we designed a series of pyridinic anticholinesterasic compounds based on molecular hybridization between tacrine and the natural piperidine alkaloid (-)-3-O-acetylspectaline isolated from Senna spectabilis. Based on the information that the cholinergic system has an important role in the treatment of schizophrenia and depression, we herein report the evaluation of a series of pyridinic compounds in animal models for antipsychotic and antidepressant-like activities. Compound 2 decreased the immobility time of mice in the forced swimming test (5 and 10mg/kg p.o.) and prevented the climbing behavior induced by apomorphine (10mg/kg, p.o.), without impairing animals locomotor activity.

Topics: Animals; Antidepressive Agents; Behavior, Animal; Central Nervous System Diseases; Disease Models, Animal; Mice; Piperidines; Pyridines; Schizophrenia

Glutamatergic dysfunction, particularly the hypofunction of N-methyl-D-aspartate (NMDA) receptors, is involved in the pathophysiology of schizophrenia. The positive modulation of the glycine site on the NMDA receptor has been proposed as a novel therapeutic approach for schizophrenia. However, its efficacy against negative symptoms, which are poorly managed by current medications, has not been fully addressed. In the present study, the effects of the positive modulation of the glycine site on the NMDA receptor were investigated in an animal model of negative symptoms of schizophrenia. The subchronic administration of MK-801 increased immobility in the forced swimming test in rats without affecting spontaneous locomotor activity. The increased immobility induced by MK-801 was attenuated by the atypical antipsychotic clozapine but not by either the typical antipsychotic haloperidol or the antidepressant imipramine, indicating that the increased immobility induced by subchronic treatment with MK-801 in the forced swimming test may represent a negative symptom of schizophrenia. Likewise, positive modulation of the glycine sites on the NMDA receptor using an agonist for the glycine site, D-serine, and a glycine transporter-1 inhibitor, N-[(3R)-3-([1,1'-biphenyl]-4-yloxy)-3-(4-fluorophenyl)propyl]-N-methylglycine hydrochloride (NFPS), significantly reversed the increase in immobility in MK-801-treated rats without reducing the immobility time in vehicle-treated rats. The present results show that the stimulation of the NMDA receptor through the glycine site on the receptor either directly with D-serine or by blocking glycine transporter-1 attenuates the immobility elicited by the subchronic administration of MK-801 and may be potentially useful for the treatment of negative symptoms of schizophrenia.

Topics: Animals; Antidepressive Agents; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Glycine; Glycine Plasma Membrane Transport Proteins; Haloperidol; Imipramine; Locomotion; Male; Motor Activity; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Sarcosine; Schizophrenia; Serine; Swimming

Dopaminergic systems have been known to be involved in the regulation of locomotor activity and development of psychosis. However, the observations that some Parkinson's disease patients can move effectively under appropriate conditions despite low dopamine levels (eg, kinesia paradoxia) and that several psychotic symptoms are typical antipsychotic resistant and atypical antipsychotic sensitive indicate that other systems beyond the dopaminergic system may also affect locomotor activity and psychosis. The present study showed that dopamine-deficient (DD) mice, which had received daily L-DOPA injections, could move effectively and even be hyperactive 72 h after the last L-DOPA injection when dopamine was almost completely depleted. Such hyperactivity was ameliorated by clozapine but not haloperidol or ziprasidone. Among multiple actions of clozapine, muscarinic acetylcholine (ACh) activation markedly reduced locomotor activity in DD mice. Furthermore, the expression of choline acetyltransferase, an ACh synthase, was reduced and extracellular ACh levels were significantly reduced in DD mice. These results suggest that the cholinergic system, in addition to the dopaminergic system, may be involved in motor control, including hyperactivity and psychosis. The present findings provide additional evidence that the cholinergic system may be targeted for the treatment of Parkinson's disease and psychosis.

Topics: Acetylcholine; Akathisia, Drug-Induced; Animals; Anti-Dyskinesia Agents; Antipsychotic Agents; Central Nervous System Stimulants; Choline O-Acetyltransferase; Clozapine; Corpus Striatum; Disease Models, Animal; Dopamine; Dopamine Agents; Extracellular Space; Haloperidol; Levodopa; Locomotion; Mice, Inbred C57BL; Piperazines; Psychomotor Agitation; Thiazoles

Depression is one of the most common chronic mental disorders, which is a leading cause of morbidity and mortality in patients. Depression often leads to offensive and defensive behaviours but the underlying mechanisms are not known. We propose that the aggressive behaviours in depression can be modelled in animal experiments. In this study, we successfully established a mouse model of depression using the chronic unpredictable mild stress (CUMS) paradigm and detected aggressive and social dominance behaviours in rodents by resident/intruder test and social dominance tube test (SDTT), respectively. The CUMS-exposed mice showed increased defensive, offensive and aggressive behaviours in the resident-intruder test. In the SDTT, these mice showed enhanced social dominance. These alterations were associated with reduced MAP-2 expression in the hippocampus while no difference in β-tubulin expression was detected. In addition, the treatment of anti-depressant fluoxetine reversed the aggressive behaviours without reducing the social dominance behaviour induced by CUMS. However, fluoxetine did effectively reverted the changes in MAP-2 expression in the hippocampus. In addition, the nonspecific tricyclic antipsychotic drug, clozapine, reversed all symptoms of CUMS-exposed mice including aggressive tendencies, impulsive violence, social dominance behaviour and MAP-2 expression in the hippocampus. The results suggests that social maladjustment such as competition and social dominance are likely related to the dopaminergic system rather than the serotonergic system and the hippocampal dendritic structure protein MAP-2. Thus, dominance can be separated from aggression. This study shows that aggression/hostility and social hierarchy/dominance are increased in the CUMS-exposed mice and thus provide an excellent model for further study in the diagnosis and the treatment of depression-associated aggression.

Topics: Aggression; Animals; Antidepressive Agents, Second-Generation; Clozapine; Depressive Disorder; Disease Models, Animal; Fluoxetine; Hippocampus; Male; Mice; Mice, Inbred C57BL; Microtubule-Associated Proteins; RNA, Messenger; Social Dominance; Stress, Psychological

Antipsychotic drugs (APs) are of great benefit in several psychiatric disorders, but they can be associated with various adverse effects, including seizures. To investigate the effects of chronic antipsychotic treatment on seizure susceptibility in genetically epilepsy-prone rats, some APs were administered for 7 weeks, and seizure susceptibility (audiogenic seizures) was evaluated once a week during treatment and for 5 weeks after drug withdrawal. Furthermore, acute and subchronic (5-day treatment) effects were also measured. Rats received haloperidol (0.2-1.0 mg/kg), clozapine (1-5 mg/kg), risperidone (0.03-0.50 mg/kg), quetiapine (2-10 mg/kg), aripriprazole (0.2-1.0 mg/kg), and olanzapine (0.13-0.66 mg/kg), and tested according to treatment duration. Acute administration of APs had no effect on seizures, whereas, after regular treatment, aripiprazole reduced seizure severity; haloperidol had no effects and all other APs increased seizure severity. In chronically treated rats, clozapine showed the most marked proconvulsant effects, followed by risperidone and olanzapine. Quetiapine and haloperidol had only modest effects, and aripiprazole was anticonvulsant. Finally, the proconvulsant effects lasted at least 2-3 weeks after treatment suspension; for aripiprazole, a proconvulsant rebound effect was observed. Taken together, these results indicate and confirm that APs might have the potential to increase the severity of audiogenic seizures but that aripiprazole may exert anticonvulsant effects. The use of APs in patients, particularly in patients with epilepsy, should be monitored for seizure occurrence, including during the time after cessation of therapy. Further studies will determine whether aripiprazole really has a potential as an anticonvulsant drug and might also be clinically relevant for epileptic patients with psychiatric comorbidities.

Topics: Animals; Antipsychotic Agents; Aripiprazole; Benzodiazepines; Clozapine; Disease Models, Animal; Epilepsy; Haloperidol; Mental Disorders; Olanzapine; Quetiapine Fumarate; Rats; Risperidone; Seizures

Safety concerns have been raised about clozapine-induced cardiotoxicity particularly in young patients. The exact mechanism of clozapine cardiotoxicity has not yet been thoroughly studied. This study aimed to investigate the possible mechanisms of clozapine-induced cardiotoxicity in a rat model. Young male Wistar rats were treated with clozapine (10, 15 and 25 mg/kg/day, i.p.) for 21 days. Haemodynamic and echocardiographic studies were performed for assessment of cardiac functions. Heart sections were studied histopathologically and immunohistochemically. Serum and cardiac markers of cardiotoxicity, oxidative stress, inflammation and apoptosis were evaluated. Heart sections of clozapine-treated animals showed increased cardiac inflammation that correlated with the clozapine dose. Serum levels of CK-MB and LDH levels increased, as did cardiac levels of TNF-α, MDA, NO, myeloperoxidase, 8-OHdG, caspase-3 and NF-κB p65. In contrast, GSH levels and GSH-Px activity decreased. Furthermore, immunohistochemical examination of the heart sections showed positive immunostaining for both 3-nitrotyrosine and caspase-3 in all clozapine-treated groups. Clozapine, particularly in relatively high doses, has a clear cardiotoxic effect. This cardiotoxicity is accompanied by increased myocardial oxidative stress, inflammatory cytokines, DNA damage and apoptosis with attenuation in antioxidant defences, thus explaining the previously reported myocarditis and pericarditis during clozapine therapy in clinical studies.

Topics: Animals; Antioxidants; Apoptosis Regulatory Proteins; Biomarkers; Clozapine; Disease Models, Animal; DNA Damage; Heart Diseases; Hemodynamics; Inflammation Mediators; Male; Myocardium; NF-kappa B; Oxidative Stress; Rats, Wistar; Signal Transduction; Tumor Necrosis Factor-alpha; Ventricular Function, Left

Designer receptors exclusively activated by designer drugs (DREADDs) are novel and powerful tools to investigate discrete neuronal populations in the brain. We have used DREADDs to stimulate degenerating neurons in a Down syndrome (DS) model, Ts65Dn mice. Individuals with DS develop Alzheimer's disease (AD) neuropathology and have elevated risk for dementia starting in their 30s and 40s. Individuals with DS often exhibit working memory deficits coupled with degeneration of the locus coeruleus (LC) norepinephrine (NE) neurons. It is thought that LC degeneration precedes other AD-related neuronal loss, and LC noradrenergic integrity is important for executive function, working memory, and attention. Previous studies have shown that LC-enhancing drugs can slow the progression of AD pathology, including amyloid aggregation, oxidative stress, and inflammation. We have shown that LC degeneration in Ts65Dn mice leads to exaggerated memory loss and neuronal degeneration. We used a DREADD, hM3Dq, administered via adeno-associated virus into the LC under a synthetic promoter, PRSx8, to selectively stimulate LC neurons by exogenous administration of the inert DREADD ligand clozapine-N-oxide. DREADD stimulation of LC-NE enhanced performance in a novel object recognition task and reduced hyperactivity in Ts65Dn mice, without significant behavioral effects in controls. To confirm that the noradrenergic transmitter system was responsible for the enhanced memory function, the NE prodrug l-threo-dihydroxyphenylserine was administered in Ts65Dn and normosomic littermate control mice, and produced similar behavioral results. Thus, NE stimulation may prevent memory loss in Ts65Dn mice, and may hold promise for treatment in individuals with DS and dementia.

Topics: Animals; Antipsychotic Agents; Cell Count; Clozapine; Cross-Over Studies; Designer Drugs; Disease Models, Animal; Down Syndrome; Exploratory Behavior; Gene Expression Regulation; Humans; Locus Coeruleus; Male; Maze Learning; Memory Disorders; Mice; Mice, Neurologic Mutants; Motor Activity; Neurodegenerative Diseases; Receptor, Muscarinic M3; Serine

NMDA receptor hypofunction could be involved, in addition to the positive, also to the negative symptoms and cognitive deficits found in schizophrenia patients. An increasing number of data has linked schizophrenia with neuroinflammatory conditions and glial cells, such as microglia and astrocytes, have been related to the pathogenesis of schizophrenia. Cannabidiol (CBD), a major non-psychotomimetic constituent of Cannabis sativa with anti-inflammatory and neuroprotective properties induces antipsychotic-like effects. The present study evaluated if repeated treatment with CBD (30 and 60 mg/kg) would attenuate the behavioral and glial changes observed in an animal model of schizophrenia based on the NMDA receptor hypofunction (chronic administration of MK-801, an NMDA receptor antagonist, for 28 days). The behavioral alterations were evaluated in the social interaction and novel object recognition (NOR) tests. These tests have been widely used to study changes related to negative symptoms and cognitive deficits of schizophrenia, respectively. We also evaluated changes in NeuN (a neuronal marker), Iba-1 (a microglia marker) and GFAP (an astrocyte marker) expression in the medial prefrontal cortex (mPFC), dorsal striatum, nucleus accumbens core and shell, and dorsal hippocampus by immunohistochemistry. CBD effects were compared to those induced by the atypical antipsychotic clozapine. Repeated MK-801 administration impaired performance in the social interaction and NOR tests. It also increased the number of GFAP-positive astrocytes in the mPFC and the percentage of Iba-1-positive microglia cells with a reactive phenotype in the mPFC and dorsal hippocampus without changing the number of Iba-1-positive cells. No change in the number of NeuN-positive cells was observed. Both the behavioral disruptions and the changes in expression of glial markers induced by MK-801 treatment were attenuated by repeated treatment with CBD or clozapine. These data reinforces the proposal that CBD may induce antipsychotic-like effects. Although the possible mechanism of action of these effects is still unknown, it may involve CBD anti-inflammatory and neuroprotective properties. Furthermore, our data support the view that inhibition of microglial activation may improve schizophrenia symptoms.

Topics: Animals; Antipsychotic Agents; Brain; Calcium-Binding Proteins; Cannabidiol; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Exploratory Behavior; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Male; Maze Learning; Mice; Mice, Inbred C57BL; Microfilament Proteins; Neuroglia; Phosphopyruvate Hydratase; Psychotic Disorders; Recognition, Psychology

Anhedonia is a relevant symptom in depression and schizophrenia. Chronic stress exposure induces in rats escape deficit, disrupts the dopaminergic response to palatable food and the competence to acquire sucrose self-administration (SA), thus configuring a possible model of motivational anhedonia. Repeated lithium administration reverts stress effects and brings back to control values the breaking point (BP) score, a measure of reward motivation. In this study, we tested on this model two antidepressants, imipramine and fluoxetine, and two antipsychotics, haloperidol and clozapine. The dopaminergic response to sucrose consumption was studied in non food-deprived rats in terms of dopamine D1 receptor signaling in the nucleus accumbens shell (NAcS). More specifically, we studied the modifications in dopamine and cAMP-regulated phosphoprotein of Mr 32,000 (DARPP-32) phosphorylation pattern following sucrose consumption. Fluoxetine reverted the escape deficit and showed no effects on dopaminergic response and sucrose SA. Imipramine reverted sucrose SA and dopamine response deficit in half of the rats and the escape deficit in all animals. Haloperidol did not affect stress-induced deficits. Clozapine-treated rats recovered the dopaminergic response to sucrose consumption and the competence to acquire sucrose SA, although they still showed the escape deficit, thus confirming that motivation toward reward may be dissociated from that to punishment escape. These results indicate that imipramine or fluoxetine are not endowed with a rapid onset antianhedonic effect. On the other hand, clozapine treatment showed a motivational antianhedonic activity similar to that observed after lithium treatment.

Topics: Anhedonia; Animals; Antidepressive Agents; Antipsychotic Agents; Clozapine; Dietary Sucrose; Disease Models, Animal; Dopamine; Dopamine and cAMP-Regulated Phosphoprotein 32; Eating; Fluoxetine; Haloperidol; Imipramine; Lithium Compounds; Male; Motivation; Nucleus Accumbens; Phosphorylation; Rats, Sprague-Dawley; Stress, Psychological

Glial cells of the central nervous system directly influence neuronal activity by releasing neuroactive small molecules, including glutamate. Long-lasting cocaine-induced reductions in extracellular glutamate in the nucleus accumbens core (NAcore) affect synaptic plasticity responsible for relapse vulnerability.. We transduced NAcore astrocytes with an adeno-associated virus vector expressing hM3D designer receptor exclusively activated by a designer drug (DREADD) under control of the glial fibrillary acidic protein promoter in 62 male Sprague Dawley rats, 4 dominant-negative soluble N-ethylmaleimide-sensitive factor attachment protein receptor mice, and 4 wild-type littermates. Using glutamate biosensors, we measured NAcore glutamate levels following intracranial or systemic administration of clozapine N-oxide (CNO) and tested the ability of systemic CNO to inhibit reinstated cocaine or sucrose seeking following self-administration and extinction training.. Administration of CNO in glial fibrillary acidic protein-hM3D-DREADD transfected animals increased NAcore extracellular glutamate levels in vivo. The glial origin of released glutamate was validated by an absence of CNO-mediated release in mice expressing a dominant-negative soluble N-ethylmaleimide-sensitive factor attachment protein receptor variant in glia. Also, CNO-mediated release was relatively insensitive to N-type calcium channel blockade. Systemic administration of CNO inhibited cue-induced reinstatement of cocaine seeking in rats extinguished from cocaine but not sucrose self-administration. The capacity to inhibit reinstated cocaine seeking was prevented by systemic administration of the group II metabotropic glutamate receptor antagonist LY341495.. DREADD-mediated glutamate gliotransmission inhibited cue-induced reinstatement of cocaine seeking by stimulating release-regulating group II metabotropic glutamate receptor autoreceptors to inhibit cue-induced synaptic glutamate spillover.

Topics: Animals; Astrocytes; Calcium Channels, N-Type; Central Nervous System Agents; Clozapine; Cocaine; Cocaine-Related Disorders; Cues; Dietary Sucrose; Disease Models, Animal; Dopamine Uptake Inhibitors; Drug-Seeking Behavior; Extinction, Psychological; Genetic Therapy; Glutamic Acid; Male; Mice, Transgenic; Nucleus Accumbens; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Receptors, Metabotropic Glutamate; Self Administration; SNARE Proteins

Altered activity of the nucleus accumbens (NAc) is thought to be a core feature of schizophrenia and animal models of the disease. Abnormal high frequency oscillations (HFO) in the rat NAc have been associated with pharmacological models of schizophrenia, in particular the N-methyl-d-aspartate receptor (NMDAR) hypofunction model. Here, we tested the hypothesis that abnormal HFO are also associated with a neurodevelopmental rat model.. Using prenatal administration of the mitotoxin methylazoxymethanol acetate (MAM) we obtained the offspring MAM rats. Adult MAM and Sham rats were implanted with electrodes, for local field potential recordings, in the NAc.. Spontaneous HFO (spHFO) in MAM rats were characterized by increased power and frequency relative to Sham rats. MK801 dose-dependently increased the power of HFO in both groups. However, the dose-dependent increase in HFO frequency found in Sham rats was occluded in MAM rats. The antipsychotic compound, clozapine reduced the frequency of HFO which was similar in both MAM and Sham rats. Further, HFO were modulated in a similar manner by delta oscillations in both MAM and Sham rats.. Together these findings suggest that increased HFO frequency represents an important feature in certain animal models of schizophrenia. These findings support the hypothesis that altered functioning of the NAc is a core feature in animal models of schizophrenia.

Topics: Animals; Antipsychotic Agents; Brain Waves; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Electroencephalography; Evoked Potentials; Excitatory Amino Acid Antagonists; Female; Male; Methylazoxymethanol Acetate; Neurotoxins; Nucleus Accumbens; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Wistar; Schizophrenia

The 14-3-3 family of proteins is implicated in the regulation of several key neuronal processes. Previous human and animal studies suggested an association between 14-3-3 dysregulation and schizophrenia.. We characterized behavioral and functional changes in transgenic mice that express an isoform-independent 14-3-3 inhibitor peptide in the brain.. We recently showed that 14-3-3 functional knockout mice (FKO) exhibit impairments in associative learning and memory. We report here that these 14-3-3 FKO mice display other behavioral deficits that correspond to the core symptoms of schizophrenia. These behavioral deficits may be attributed to alterations in multiple neurotransmission systems in the 14-3-3 FKO mice. In particular, inhibition of 14-3-3 proteins results in a reduction of dendritic complexity and spine density in forebrain excitatory neurons, which may underlie the altered synaptic connectivity in the prefrontal cortical synapse of the 14-3-3 FKO mice. At the molecular level, this dendritic spine defect may stem from dysregulated actin dynamics secondary to a disruption of the 14-3-3-dependent regulation of phosphorylated cofilin.. Collectively, our data provide a link between 14-3-3 dysfunction, synaptic alterations, and schizophrenia-associated behavioral deficits.

Topics: 14-3-3 Proteins; Animals; Antipsychotic Agents; Behavior, Animal; Catenins; Cerebral Cortex; Clozapine; Cofilin 1; Delta Catenin; Dendrites; Disease Models, Animal; Dopamine; Haloperidol; Mice; Mice, Inbred C57BL; Mice, Knockout; Phenotype; Prepulse Inhibition; Proteins; Receptors, Dopamine; Schizophrenia; Schizophrenic Psychology; Synaptic Transmission

Oxidative stress has important implications in schizophrenia. Alpha-lipoic acid (ALA) is a natural antioxidant synthesized in human tissues with clinical uses. We studied the effect of ALA or clozapine (CLZ) alone or in combination in the reversal of schizophrenia-like alterations induced by ketamine (KET). Adult male mice received saline or KET for 14 days. From 8th to 14th days mice were additionally administered saline, ALA (100 mg/kg), CLZ 2.5 or 5 mg/kg or the combinations ALA+CLZ2.5 or ALA+CLZ5. Schizophrenia-like symptoms were evaluated by prepulse inhibition of the startle (PPI) and locomotor activity (positive-like), social preference (negative-like) and Y maze (cognitive-like). Oxidative alterations (reduced glutathione - GSH and lipid peroxidation - LP) and nitrite in the prefrontal cortex (PFC), hippocampus (HC) and striatum (ST) and BDNF in the PFC were also determined. KET caused deficits in PPI, working memory, social interaction and hyperlocomotion. Decreased levels of GSH, nitrite (HC) and BDNF and increased LP were also observed in KET-treated mice. ALA and CLZ alone reversed KET-induced behavioral alterations. These drugs also reversed the decreases in GSH (HC) and BDNF and increase in LP (PFC, HC and ST). The combination ALA+CLZ2.5 reversed behavioral and some neurochemical parameters. However, ALA+CLZ5 caused motor impairment. Therefore, ALA presented an antipsychotic-like profile reversing KET-induced positive- and negative-like symptoms. The mechanism partially involves antioxidant, neurotrophic and nitrergic pathways. The combination of ALA+CLZ2.5 improved most of the parameters evaluated in this study without causing motor impairment demonstrating, thus, that possibly when combined with ALA a lower dose of CLZ is required.

Topics: Analysis of Variance; Animals; Antioxidants; Antipsychotic Agents; Brain; Brain-Derived Neurotrophic Factor; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Therapy, Combination; Enzyme-Linked Immunosorbent Assay; Excitatory Amino Acid Antagonists; Exploratory Behavior; Glutathione; Interpersonal Relations; Ketamine; Lipid Peroxidation; Male; Malondialdehyde; Maze Learning; Mice; Nitrites; Random Allocation; Reflex, Startle; Schizophrenia; Thioctic Acid

Modulating the methylation process induces broad biochemical changes, some of which may be involved in schizophrenia. Methylation is in particular central to epigenesis, which is also recognized as a factor in the etiology of schizophrenia. Because methionine administration to patients with schizophrenia has been reported to exacerbate their psychotic symptoms and because mice treated with methionine exhibited social deficits and prepulse inhibition impairment, we investigated whether methionine administration could lead to behavioral changes that reflect schizophrenic symptoms in mice.. l-Methionine was administered to mice twice a day for 7 days.. We found that this treatment induces behavioral responses that reflect the 3 types of schizophrenia-like symptoms (positive, negative, or cognitive deficits) as monitored in a battery of behavioral assays (locomotion, stereotypy, social interaction, forced swimming, prepulse inhibition, novel object recognition, and inhibitory avoidance). Moreover, these responses were differentially reversed by typical haloperidol and atypical clozapine antipsychotics in ways that parallel their effects in schizophrenics.. We thus propose the l-methionine treatment as an animal model recapitulating several symptoms of schizophrenia. We have established the face and predictive validity for this model. Our model relies on an essential natural amino acid and on an intervention that is relatively simple and time effective and may offer an additional tool for assessing novel antipsychotics.

Topics: Animals; Antipsychotic Agents; Avoidance Learning; Clozapine; Depression; Disease Models, Animal; Haloperidol; Male; Methionine; Mice; Motor Activity; Pain Threshold; Recognition, Psychology; Schizophrenia; Schizophrenic Psychology; Sensory Gating; Social Behavior; Stereotyped Behavior; Treatment Outcome

Metabolic syndrome is a major concern in psychotic patients receiving atypical antipsychotics. Recent evidence suggests that sterol regulatory element-binding proteins (SREBPs) and insulin-induced genes (INSIGs) are implicated in the antipsychotic-induced metabolic side-effects. Vitamin D (VD) deficiency, a highly prevalent phenomenon among patients with psychosis, might also predispose individuals to metabolic syndrome Considering that VD has modulating effects on the INSIG/SREBP pathway, it is possible that VD may have a role in the antipsychotic-induced metabolic disturbances involving its effects on the INSIG/SREBP system. Thus, the present study aimed to evaluate the effects of VD deficiency and VD supplementation on antipsychotic-induced metabolic changes in rats. After 4-week administration, clozapine (10mg/kg/d) and risperidone (1mg/kg/d) both caused glucose intolerance and insulin resistance in VD deficient rats, but not in rats with sufficient VD status. Antipsychotic treatments, especially clozapine, elevated serum lipid levels, which were most apparent in VD deficient rats, but alleviated in VD-supplemented rats. Additionally, antipsychotic treatments down-regulated INSIGs and up-regulated SREBPs expression in VD deficient rats, and these effects were attenuated when VD status was more sufficient. Collectively, this study disclose the novel findings that antipsychotic-induced metabolic disturbances is exacerbated by VD deficiency and can be alleviated by VD supplementation, providing new evidence for the promising role of VD in prevention and treatment of metabolic disorders caused by antipsychotic medications. Furthermore, our data also suggest the involvement of INSIG/SREBP pathway in the antipsychotic-induced hyperlipidemia and beneficial effects of VD on lipid profile.

Topics: Animals; Antipsychotic Agents; Body Weight; Clozapine; Disease Models, Animal; Eating; Glucose Intolerance; Glucose Tolerance Test; Insulin Resistance; Intra-Abdominal Fat; Male; Random Allocation; Rats, Sprague-Dawley; Risperidone; Vitamin D Deficiency

The Spontaneously Hypertensive Rat (SHR) strain is a classical animal model for the study of essential hypertension. Recently, our group suggested that this strain could be a useful animal model for schizophrenia, which is a severe mental illness with involvement of glutamatergic system. The aim of this study is to investigate glutamatergic receptors (Gria1 and Grin1) and glycine transporter (Glyt1) gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) of SHR animals. The effects in gene expression of a chronic treatment with antipsychotic drugs (risperidone, haloperidol and clozapine) were also analyzed. Animals were treated daily for 30 days, and euthanized for brain tissue collection. The expression pattern was evaluated by Real Time Reverse-Transcriptase (RT) PCR technique. In comparison to control rats, SHR animals present a lower expression of both NMDA (Grin1) and AMPA (Gria1) gene receptors in the NAcc. Antipsychotic treatments were not able to change gene expressions in any of the regions evaluated. These findings provide evidence for the role of glutamatergic changes in schizophrenia-like phenotype of the SHR strain.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Gene Expression; Glycine Plasma Membrane Transport Proteins; Haloperidol; Male; Nucleus Accumbens; Prefrontal Cortex; Rats; Rats, Inbred SHR; Receptors, AMPA; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Reverse Transcriptase Polymerase Chain Reaction; Risperidone; Schizophrenia

Previous findings suggested that a four-protein complex, including sterol-regulatory element-binding protein (SREBP), SREBP-cleavage-activating protein (SCAP), insulin-induced gene (INSIG) and progesterone receptor membrane component 1 (PGRMC1), within the endoplasmic reticulum appears to be an important regulator responsible for atypical antipsychotic drug (AAPD)-induced lipid disturbances. In the present study, effects of typical antipsychotic drug and AAPDs as well as treatment outcome of steroid antagonist mifepristone (MIF) on the PGRMC1/INSIG/SCAP/SREBP pathway were investigated in rat liver using real-time quantitative polymerase chain reaction (qPCR) and western blot analysis. In addition, serum triacylglycerol, total cholesterol, free fatty acids and various hormones including progesterone, corticosterone and insulin were measured simultaneously. Following treatment with clozapine or risperidone, both lipogenesis and cholesterogenesis were enhanced via inhibition of PGRMC1/INSIG-2 and activation of SCAP/SREBP expressions. Such metabolic disturbances, however, were not demonstrated in rats treated with aripiprazole (ARI) or haloperidol (HAL). Moreover, the add-on treatment of MIF was effective in reversing the AAPD-induced lipid disturbances by upregulating the expression of PGRMC1/INSIG-2 and subsequent downregulation of SCAP/SREBP. Taken together, our findings suggest that disturbances in lipid metabolism can occur at an early stage of AAPD treatment before the presence of weight gain. Such metabolic defects can be modified by an add-on treatment of steroid antagonist MIF enhancing the PGRMC1 pathway. Thus, it is likely that PGRMC1/INSIG-2 signaling may be a therapeutic target for AAPD-induced weight gain.

Topics: Animals; Antipsychotic Agents; Blotting, Western; Cholesterol; Clozapine; Corticosterone; Disease Models, Animal; Fatty Acids, Nonesterified; Insulin; Lipid Metabolism; Lipogenesis; Liver; Male; Polymerase Chain Reaction; Progesterone; Rats; Rats, Sprague-Dawley; Risperidone; Signal Transduction; Triglycerides

The factors causing the transition from recreational drug consumption to addiction remain largely unknown. It has not been tested whether dopamine (DA) is sufficient to trigger this process. Here we use optogenetic self-stimulation of DA neurons of the ventral tegmental area (VTA) to selectively mimic the defining commonality of addictive drugs. All mice readily acquired self-stimulation. After weeks of abstinence, cue-induced relapse was observed in parallel with a potentiation of excitatory afferents onto D1 receptor-expressing neurons of the nucleus accumbens (NAc). When the mice had to endure a mild electric foot shock to obtain a stimulation, some stopped while others persevered. The resistance to punishment was associated with enhanced neural activity in the orbitofrontal cortex (OFC) while chemogenetic inhibition of the OFC reduced compulsivity. Together, these results show that stimulating VTA DA neurons induces behavioral and cellular hallmarks of addiction, indicating sufficiency for the induction and progression of the disease.

Topics: Animals; Channelrhodopsins; Clozapine; Cocaine; Cocaine-Related Disorders; Conditioning, Operant; Disease Models, Animal; Dopamine Plasma Membrane Transport Proteins; Dopamine Uptake Inhibitors; Dopaminergic Neurons; Food Deprivation; GABA Antagonists; Glutamate Decarboxylase; Limbic System; Mice; Mice, Inbred C57BL; Mice, Transgenic; Receptors, Dopamine D1; Self Administration; Sucrose; Synaptic Transmission; Time Factors

Despite the well-established role of serotonin signaling in mood regulation, causal relationships between serotonergic neuronal activity and behavior remain poorly understood. Using a pharmacogenetic approach, we find that selectively increasing serotonergic neuronal activity in wild-type mice is anxiogenic and reduces floating in the forced-swim test, whereas inhibition has no effect on the same measures. In a developmental mouse model of altered emotional behavior, increased anxiety and depression-like behaviors correlate with reduced dorsal raphé and increased median raphé serotonergic activity. These mice display blunted responses to serotonergic stimulation and behavioral rescues through serotonergic inhibition. Furthermore, we identify opposing consequences of dorsal versus median raphé serotonergic neuron inhibition on floating behavior, together suggesting that median raphé hyperactivity increases anxiety, whereas a low dorsal/median raphé serotonergic activity ratio increases depression-like behavior. Thus, we find a critical role of serotonergic neuronal activity in emotional regulation and uncover opposing roles of median and dorsal raphé function.

Topics: Animals; Anxiety; Behavior, Animal; Cell Line; Clozapine; Depressive Disorder; Disease Models, Animal; Female; Male; Mice; Mice, Transgenic; Serotonergic Neurons; Serotonin; Swimming

Depression interferes with the human ability to make decisions. Multiple criteria have been adopted for the diagnosis of depression in humans, but no clear indicators are available in animal models to reflect the depressive mood, involving higher cognitive functions. The act of foraging is a species-specific behaviour which is believed to involve the decision-making and higher cognitive functions. We previously established a method to detect the foraging behaviour of rodents, in which our results demonstrated that NMDA and dopamine receptors were involved. Conversely, increased NMDA receptors and reduced dopamine have been reported in depression model rodents. However, we hypothesise that foraging activities may also be impaired in depression. To test the theory, we successfully established a mouse model of depression using the chronic unpredictable mild stress (CUMS) paradigm. Most interestingly, the food foraging activity of mice after CUMS was significantly reduced. In addition, the treatment of anti-depressant fluoxetine reversed most depressive symptoms and reduced glial fibrillary associated protein (GFAP) expression in the hippocampus, but was less effective in the reduction of foraging activities. However, clozapine reversed all symptoms of CUMS-exposed mice including reduction of GFAP expression in the hippocampus and impaired foraging activity. Our findings of GFAP expression as a marker to validate the CUMS protocol provide further validation of our hypothesis, that the reduced food foraging is probably a new behavioural finding of depression in which the serotoninergic system could not be singly involved. Our study suggests that NMDA receptors, serotoninergic and dopaminergic systems are differentially involved in these food foraging behaviours. Our data suggest that the foraging test in rodents can be a useful tool to assess the ability of decision-making in depression.

Topics: Animals; Antidepressive Agents; Appetitive Behavior; Body Weight; Cerebral Cortex; Chronic Disease; Clozapine; Depressive Disorder; Disease Models, Animal; Exploratory Behavior; Feeding Behavior; Fluoxetine; Freezing Reaction, Cataleptic; Glial Fibrillary Acidic Protein; Hippocampus; Male; Mice; Mice, Inbred C57BL; RNA, Messenger; Stress, Psychological

Psychiatric disorders have been hypothesized to originate during development, with genetic and environmental factors interacting in the etiology of disease. Therefore, developmentally regulated genes have received attention as risk modulators in psychiatric diseases. Reelin is an extracellular protein essential for neuronal migration and maturation during development, and its expression levels are reduced in psychiatric disorders. Interestingly, several perinatal insults that increase the risk of behavioral deficits alter Reelin signaling. However, it is not known whether a dysfunction in Reelin signaling during perinatal stages increases the risk of psychiatric disorders. Here we used a floxed dab1 allele to study whether a transient decrease in Dab1, a key component of the Reelin pathway, is sufficient to induce behavioral deficits related to psychiatric disorders. We found that transient Dab1 downregulation during perinatal stages leads to permanent abnormalities of structural layering in the neocortex and hippocampus. In contrast, conditional inactivation of the dab1 gene in the adult brain does not result in additional layering abnormalities. Furthermore, perinatal Dab1 downregulation causes behavior impairments in adult mice, such as deficits in memory, maternal care, pre-pulse inhibition, and response to cocaine. Some of these deficits were also found to be present in adolescence. We also show that D-cycloserine rescues the cognitive deficits observed in floxed dab1 mice with layering alterations in the hippocampus and neocortex. Our results indicate a causal relation between the downregulation of Dab1 protein levels during development and the structural and behavioral deficits associated with psychiatric diseases in the adult.

Topics: Animals; Animals, Newborn; Antipsychotic Agents; beta-Galactosidase; Brain; Clozapine; Corticosterone; Disease Models, Animal; Down-Regulation; Female; Gene Expression Regulation, Developmental; Male; Mental Disorders; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Activity; Mutation; Nerve Tissue Proteins; Reelin Protein; Tamoxifen

Typical and atypical antipsychotics have been shown to alleviate N-methyl-D-aspartate (NMDA) receptor antagonist-induced BOLD signals in healthy humans and animals to differing degrees; factors that might relate to their different molecular mechanisms and clinical profiles. Recent studies have also extended these investigations to the analysis of resting state functional connectivity measures of BOLD signals in different brain regions. Using constant potential amperometry, we examined the effects of the NMDA receptor antagonist S-(+)-ketamine on tissue oxygen levels in medial prefrontal cortex (mPFC) and medial ventral striatum (mVS), and temporal coherence of low-frequency oxygen fluctuations between these regions in freely moving rats. Furthermore, we assessed the extent to which the atypical antipsychotic clozapine and the typical antipsychotic haloperidol could modulate the effects of S-(+)-ketamine on these measures. Acute S-(+)-ketamine (5-25 mg/kg) produced dose-dependent increases in both tissue O2 levels and coherence. Although effects of clozapine and haloperidol alone were relatively minor, their effects on ketamine-induced signals were markedly more distinct. Clozapine dose-dependently attenuated the absolute S-(+)-ketamine (25 mg/kg) O2 signal in both regions, and also attenuated ketamine-induced increases in regional coherence. Haloperidol had no effect on the absolute ketamine O2 signal yet potentiated increases in regional coherence. The dissociable effects of haloperidol and clozapine on ketamine-induced hyperoxygenation and mPFC-mVS coherence elucidate potentially important mechanistic differences between these classes of pharmacology. This study demonstrates for the first time that in vivo amperometry can measure both regional brain tissue O2 levels and inter-regional coherence, advancing BOLD-like measurements of functional connectivity into awake, unconstrained animals.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Area Under Curve; Brain; Clozapine; Disease Models, Animal; Dissociative Disorders; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Haloperidol; Ketamine; Male; Oxygen; Rats; Tissue Distribution

Dopamine neurons in the ventral tegmental area (VTA) govern reward and motivation and dysregulated dopaminergic transmission may account for anhedonia and other symptoms of depression. Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase that regulates a broad range of brain functions through phosphorylation of a myriad of substrates, including tyrosine hydroxylase (TH), the rate-limiting enzyme for dopamine synthesis. We investigated whether and how Cdk5 activity in VTA dopamine neurons regulated depression-related behaviors in mice. Using the Cre/LoxP system to selectively delete Cdk5 in the VTA or in midbrain dopamine neurons in Cdk5(loxP/loxP) mice, we showed that Cdk5 loss of function in the VTA induced anxiety- and depressive-like behaviors that were associated with decreases in TH phosphorylation at Ser31 and Ser40 in the VTA and dopamine release in its target region, the nucleus accumbens. The decreased phosphorylation of TH at Ser31 was a direct effect of Cdk5 deletion, whereas decreased phosphorylation of TH at Ser40 was likely caused by impaired cAMP/protein kinase A (PKA) signaling, because Cdk5 deletion decreased cAMP and phosphorylated cAMP response element-binding protein (p-CREB) levels in the VTA. Using Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology, we showed that selectively increasing cAMP levels in VTA dopamine neurons increased phosphorylation of TH at Ser40 and CREB at Ser133 and reversed behavioral deficits induced by Cdk5 deletion. The results suggest that Cdk5 in the VTA regulates cAMP/PKA signaling, dopaminergic neurotransmission, and depression-related behaviors.

Topics: Animals; Antipsychotic Agents; Clozapine; CREB-Binding Protein; Cyclic AMP; Cyclin-Dependent Kinase 5; Depression; Disease Models, Animal; Dopamine Plasma Membrane Transport Proteins; Exploratory Behavior; Food Preferences; Green Fluorescent Proteins; In Vitro Techniques; Maze Learning; Mice; Mice, Inbred C57BL; Mice, Transgenic; RNA, Untranslated; Serine; Ventral Tegmental Area

Tardive dyskinesia (TD) is a delayed and potentially irreversible motor complication arising in patients chronically exposed to centrally active dopamine D2 receptor antagonists, including antipsychotic drugs and metoclopramide. The classical dopamine D2 receptor supersensitivity hypothesis in TD, which stemmed from rodent studies, lacks strong support in humans. To investigate the neurochemical basis of TD, we chronically exposed adult capuchin monkeys to haloperidol (median, 18.5 months; n = 11) or clozapine (median, 6 months; n = 6). Six unmedicated animals were used as controls. Five haloperidol-treated animals developed mild TD movements, and no TD was observed in the clozapine group. Using receptor autoradiography, we measured striatal dopamine D1, D2, and D3 receptor levels. We also examined the D3 receptor/preprotachykinin messenger RNA (mRNA) co-expression, and quantified preproenkephalin mRNA levels, in striatal sections. Unlike clozapine, haloperidol strongly induced dopamine D3 receptor binding sites in the anterior caudate-putamen, particularly in TD animals, and binding levels positively correlated with TD intensity. Interestingly, the D3 receptor upregulation was observed in striatonigral neurons. In contrast, D2 receptor binding was comparable to controls, and dopamine D1 receptor binding was reduced in the anterior putamen. Enkephalin mRNA widely increased in all animals, but to a greater extent in TD-free animals. These results suggest for the first time that upregulated striatal D3 receptors correlate with TD in nonhuman primates, adding new insights to the dopamine receptor supersensitivity hypothesis. The D3 receptor could provide a novel target for drug intervention in human TD.

Topics: Animals; Antipsychotic Agents; Brain; Cebus; Clozapine; Disease Models, Animal; Dopamine Antagonists; Enkephalins; Female; Haloperidol; Iodine Radioisotopes; Movement Disorders; Neurons; Ovariectomy; Protein Binding; Receptors, Dopamine D2; Receptors, Dopamine D3; Sulpiride; Tetrahydronaphthalenes; Up-Regulation

Antipsychotic drugs (APDs) are the standard treatment for schizophrenia. The therapeutic effect of these drugs is dependent upon the dopaminergic D2 blockade, but they also modulate other neurotransmitter pathways. The exact mechanisms underlying the clinical response to APDs are not fully understood. In this study, we compared three groups of animals for the expression of 84 neurotransmitter genes in the prefrontal cortex (PFC) and nucleus accumbens (NAcc). Each group was treated with a different APD (risperidone, clozapine or haloperidol), and with a non-treated group of spontaneously hypertensive rats (SHRs), which is an animal model for schizophrenia. This study also explored whether or not differential expression was regulated by DNA methylation in the promoter region (PR). In the clozapine group, we found that Chrng was downregulated in the NAcc and six genes were downregulated in the PFC. In the haloperidol group, Brs3 and Glra1 were downregulated, as was Drd2 in the clozapine group and Drd3, Galr3 and Gabrr1 in the clozapine and haloperidol groups. We also encountered four hypermethylated CG sites in the Glra1 PR, as well as three in the risperidone group and another in the haloperidol group, when compared to non-treated rats. Following the APD treatment, the gene expression results revealed the involvement of genes that had not previously been described, in addition to the activity of established genes. The investigation of the involvement of these novel genes can lead to better understanding about the specific mechanisms of action of the individual APDs studied.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; DNA Methylation; Gene Expression; Haloperidol; Male; Neurotransmitter Agents; Nucleus Accumbens; Prefrontal Cortex; Promoter Regions, Genetic; Rats, Inbred SHR; Risperidone; Schizophrenia

Studies in humans indicate that acute administration of sub-anesthetic doses of ketamine, an NMDA receptor antagonist, provokes schizophrenic-like symptoms in healthy volunteers, and exacerbates existing symptoms in individuals with schizophrenia. These and other findings suggest that NMDA receptor hypofunction might participate in the pathophysiology of schizophrenia, and have prompted the development of rodent pharmacological models for this disorder based on acute or subchronic treatment with NMDA receptor antagonists, as well as the development of novel pharmacotherapies based on increasing extrasynaptic glycine concentrations. In the present study, we tested whether acute hyperlocomotory behavior and/or deficits in the novel object recognition (NOR) task, induced in male rabbits by the acute subcutaneous (s.c.) administration of MK-801 (0.025 and 0.037 mg/kg s.c., respectively), were prevented by prior administration of the atypcial antipsychotic, clozapine (0.2mg/kg, s.c.), or the glycine pro-drug glycinamide (56 mg/kg, s.c.). We found that clozapine fully prevented the MK-801-induced hyperlocomotion, and both clozapine and glycinamide prevented MK-801-induced deficits in the NOR task. The present results show that MK-801-induced hyperlocomotion and deficits in the NOR task in the domestic rabbit demonstrate predictive validity as an alternative animal model for symptoms of schizophrenia. Moreover, these results indicate that glycinamide should be investigated in pre-clinical models of neuropsychiatric disorders such as schizophrenia, obsessive compulsive disorder and anxiety disorders, where augmentation of extrasynaptic glycine concentrations may have therapeutic utility.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Exploratory Behavior; Glycine; Locomotion; Male; Rabbits; Receptors, N-Methyl-D-Aspartate; Recognition, Psychology; Schizophrenia; Schizophrenic Psychology; Treatment Outcome; Visual Perception

Direct lineage reprogramming through genetic-based strategies enables the conversion of differentiated somatic cells into functional neurons and distinct neuronal subtypes. Induced dopaminergic (iDA) neurons can be generated by direct conversion of skin fibroblasts; however, their in vivo phenotypic and functional properties remain incompletely understood, leaving their impact on Parkinson's disease (PD) cell therapy and modeling uncertain. Here, we determined that iDA neurons retain a transgene-independent stable phenotype in culture and in animal models. Furthermore, transplanted iDA neurons functionally integrated into host neuronal tissue, exhibiting electrically excitable membranes, synaptic currents, dopamine release, and substantial reduction of motor symptoms in a PD animal model. Neuronal cell replacement approaches will benefit from a system that allows the activity of transplanted neurons to be controlled remotely and enables modulation depending on the physiological needs of the recipient; therefore, we adapted a DREADD (designer receptor exclusively activated by designer drug) technology for remote and real-time control of grafted iDA neuronal activity in living animals. Remote DREADD-dependent iDA neuron activation markedly enhanced the beneficial effects in transplanted PD animals. These data suggest that iDA neurons have therapeutic potential as a cell replacement approach for PD and highlight the applicability of pharmacogenetics for enhancing cellular signaling in reprogrammed cell-based approaches.

Topics: Animals; Brain; Cell Transdifferentiation; Clozapine; Designer Drugs; Disease Models, Animal; Dopamine; Dopaminergic Neurons; Electrophysiological Phenomena; Female; Humans; Male; Mice; Mice, Knockout; Parkinsonian Disorders; Rats; Rats, Transgenic

A large percentage of schizophrenic patients respond poorly to antipsychotic treatment. This could be explained by inefficient drug transport across the blood-brain barrier due to P-glycoprotein mediated efflux. P-glycoprotein activity and expression in the blood-brain barrier can be affected by inflammation and pharmacotherapy. We therefore investigated the effect of herpes simplex virus type-1 (HSV-1) induced neuroinflammation and antipsychotic treatment on P-glycoprotein activity. Rats were inoculated with HSV-1 or PBS (control) on day 0 and treated with saline, clozapine or risperidone from day 0 up until day 4 post-inoculation. Positron emission tomography with the P-glycoprotein substrate [11C]verapamil was used to assess P-glycoprotein activity at day 6 post-inoculation. Disease symptoms in HSV-1 inoculated rats increased over time and were not significantly affected by treatment. The volume of distribution (VT) of [11C]verapamil was significantly lower (10-22%) in HSV-1 inoculated rats than in control rats. In addition, antipsychotic treatment significantly affected the VT of [11C]verapamil in all brain regions, although this effect was drug dependent. In fact, VT of [11C]verapamil was significantly increased (22-39%) in risperidone treated rats in most brain regions when compared to clozapine treated rats and in midbrain when compared to saline treated rats. No interaction between HSV-1 inoculation and antipsychotic treatment on VT of [11C]verapamil was found. In this study we demonstrated that HSV-1 induced neuroinflammation increased and risperidone treatment decreased P-glycoprotein activity. This finding is of importance for the understanding of treatment resistance in schizophrenia, and warrants further investigation of the underlying mechanism and the importance in clinical practice.

Topics: Animals; Antipsychotic Agents; ATP Binding Cassette Transporter, Subfamily B; Blood-Brain Barrier; Brain; Carbon Radioisotopes; Clozapine; Disease Models, Animal; Herpes Simplex; Herpesvirus 1, Human; Male; Neuroimmunomodulation; Positron-Emission Tomography; Radiopharmaceuticals; Random Allocation; Rats, Wistar; Risperidone; Verapamil

Rheumatoid arthritis is a widespread autoimmune disease. In the murine K/B×N arthritis model, anti-GPI (anti-glucose 6-phosphate isomerase) antibodies lead to the formation of immune complexes. In the course of pathogenesis, these complexes activate the immune system and induce degranulation of mast cells, which are essential in this model of rheumatoid arthritis. A major mediator in mast cell granules is histamine, which is proven to be indispensable for joint inflammation in K/B×N mice. Histamine is known to bind to four different receptors (HR1-4), which have different expression profiles and exert a variety of different functions, including activation of the immune system. To analyze the contribution of the different histamine receptors, we employed histamine receptor antagonists (cetirizine, ranitidine, thioperamide and clozapine) blocking the receptors in C57BL/6 mice. Arthritis was induced via K/B×N serum injection. The results demonstrated that mice treated with all four histamine receptor antagonists simultaneously showed no arthritic symptoms, while positive control mice injected with K/B×N serum and vehicle suffered from severe symptoms. When antagonists specific for HR1-4 were applied individually, only the HR4 antagonist clozapine could protect mice from arthritis, reflecting its expression and functionality in the immune system.

Topics: Animals; Arthritis, Rheumatoid; Autoantibodies; Autoimmune Diseases; Clozapine; Disease Models, Animal; Glucose-6-Phosphate Isomerase; Histamine Antagonists; Mice; Mice, Inbred C57BL; Mice, Inbred NOD; Mice, Transgenic; Receptors, G-Protein-Coupled; Receptors, Histamine; Receptors, Histamine H4

Schizophrenia, described as the worst disease affecting mankind, is a severe and disabling mental disorder. Schizophrenia is characterized by complicated symptoms and still lacks a diagnostic neuropathology, so developing schizophrenia animal models which have quantifiable measures tested in a similar fashion in both humans and animals will play a key role in new therapeutic approaches. According to the symptoms of cognitive impairment and emotional disorder, the N-methyl-d-aspartate (NMDA)-receptor antagonist MK-801 was applied to induce schizophrenia-like behavior in mice. Locomotor activity and prepulse inhibition (PPI) were selected as indices and the effect of clozapine was also investigated in this model. The results showed that compared with the normal group, MK-801-treated mice exhibited significantly increased locomotor activity and impaired PPI, and pre-exposure to clozapine could ameliorate the abnormality and make it back to normal level. These findings suggest that the model we established could be a useful tool for antipsychotic drug screening.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Inhibition, Psychological; Male; Mice; Motor Activity; Receptors, N-Methyl-D-Aspartate; Schizophrenia

Deficient sensory inhibition, the failure to inhibit responses to repeated stimuli, is a hallmark of schizophrenia, and is thought to be related to difficulties with attention and working memory. Sensory inhibition is assessed by comparing the auditory-evoked EEG responses to 2 closely-spaced identical stimuli. Normal individuals show suppressed response to the second stimulus while schizophrenia patients have responses of similar magnitude to both stimuli. This deficit has been linked to polymorphisms in the promoter for the α7 nicotinic receptor gene, resulting in reduced numbers of receptors on hippocampal interneurons. This deficit is modeled in DBA/2 mice which also show a polymorphism in the promoter for the α7 nicotinic receptor gene and reduced numbers of hippocampal α7 receptors. Systemic administration of clozapine, the most efficacious antipsychotic medication, improves sensory inhibition deficits in both schizophrenia patients and DBA/2 mice. We have previously shown that acute intracerebroventricular (ICV) injections of clozapine induced similar improvement in sensory inhibition in DBA/2 mice. Here we demonstrate the efficacy of chronic ICV clozapine administration in improving sensory inhibition in DBA2 mice. Mice received ICV vehicle, 3, 7.5, 15 or 30 μg of clozapine, either continuously or as a once-per-day injection. Mice were recorded on the 7th day of drug delivery. Both approaches produced improved sensory inhibition, but the daily bolus injection was effective at a lower dose (3 μg/day) than the continuous delivery (15 μg/day). The bolus injections also showed significant improvement up to 36 h post injection thus suggesting that this approach may be more efficacious.

Topics: Acoustic Stimulation; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Routes; Drug Delivery Systems; Electroencephalography; Evoked Potentials, Auditory; Gait Disorders, Neurologic; Mice; Mice, Inbred DBA; Multivariate Analysis; Neural Inhibition; Sensory Gating; Time Factors

Previous research demonstrates that disruption of forebrain dopamine systems impairs the use of high-order information to guide goal-directed performance, and that this deficit may be related to impaired use of task-setting cues in patients with schizophrenia. Such deficits can be interrogated through conflict resolution, which has been demonstrated to be sensitive to prefrontal integrity in rodents. We sought to examine the effects of acute systemic d-amphetamine administration on the contextual control of response conflict in rats, and whether deficits were reversed through pre-treatment with clozapine or the D₁/D₂ antagonist α-flupenthixol. Acute d-amphetamine (1.5 mg/kg) disrupted the utilisation of contextual cues; therefore rats were impaired during presentation of stimulus compounds that require conflict resolution. Evidence suggested that this effect was attenuated through pre-treatment with the atypical antipsychotic clozapine (5.0 mg/kg), but not the typical antipsychotic α-flupenthixol (0.25 mg/kg), at doses previously shown to attenuate d-amphetamine-induced cognitive deficits. These studies therefore demonstrate a potentially viable model of disrupted executive function such as that seen in schizophrenia.

Topics: Animals; Antipsychotic Agents; Central Nervous System Stimulants; Clozapine; Conditioning, Operant; Cues; Dextroamphetamine; Discrimination, Psychological; Disease Models, Animal; Flupenthixol; Male; Negotiating; Rats; Schizophrenic Psychology

Schizophrenia was proposed as a progressive neurodevelopmental disorder. In this regard herein we attempted to determine progressive inflammatory and oxidative alterations induced by a neonatal immune challenge and its possible reversal by clozapine administration. For this end, Wistar rats at postnatal day (PN) 5-7 were administered the viral mimetic polyriboinosinic-polyribocytidilic acid (polyI:C) or saline. A distinct group of animals additionally received the antipsychotic drug clozapine (25mg/kg) from PN60 to 74. At PN35 (periadolescence), 60 (adult) and 74 (adulthood) the animals were submitted to behavioral determinations of prepulse inhibition of the startle (PPI) and Y maze task for working memory evaluation. At PN35 and 74 the animals were sacrificed and the hippocampus (HC), prefrontal cortex (PFC) and striatum (ST) immunostained for Iba-1, a microglial marker, and inducible nitric oxide synthase (iNOS). At PN74 oxidative stress parameters, such as, reduced glutathione levels (GSH) and lipid peroxidation were determined. The results showed a progressive increase of microglial activation and iNOS immunostaining from PN35 to PN74 mainly in the CA2 and CA3 regions of the HC and in the ST. At PN74 neonatal challenge also induced an oxidative imbalance. These inflammatory alterations were accompanied by deficits in PPI and working memory only in adult life that were reversed by clozapine. Clozapine administration reversed microglial activation and iNOS increase, but not the alterations of oxidative stress parameters. Taken together these results give further evidences for a neuroprogressive etiology and course of schizophrenia and that clozapine may partly alleviate this process.

Topics: Age Factors; Animals; Animals, Newborn; Antipsychotic Agents; Brain; Clozapine; Developmental Disabilities; Disease Models, Animal; Lipid Peroxidation; Male; Malondialdehyde; Maze Learning; Microglia; Nitric Oxide Synthase Type II; Oxidative Stress; Poly I-C; Rats; Rats, Wistar; Reflex, Startle; Schizophrenia

Dopamine (DA) neurotransmission requires a complex series of enzymatic reactions that are tightly linked to catecholamine exocytosis and receptor interactions on pre- and postsynaptic neurons. Regulation of dopaminergic signalling is primarily achieved through reuptake of extracellular DA by the DA transporter (DAT) on presynaptic neurons. Aberrant regulation of DA signalling, and in particular hyperactivation, has been proposed as a key insult in the presentation of schizophrenia and related neuropsychiatric disorders. We recently identified 14-3-3ζ as an essential component of neurodevelopment and a central risk factor in the schizophrenia protein interaction network. Our analysis of 14-3-3ζ-deficient mice now shows that baseline hyperactivity of knockout (KO) mice is rescued by the antipsychotic drug clozapine. 14-3-3ζ KO mice displayed enhanced locomotor hyperactivity induced by the DA releaser amphetamine. Consistent with 14-3-3ζ having a role in DA signalling, we found increased levels of DA in the striatum of 14-3-3ζ KO mice. Although 14-3-3ζ is proposed to modulate activity of the rate-limiting DA biosynthesis enzyme, tyrosine hydroxylase (TH), we were unable to identify any differences in total TH levels, TH localization or TH activation in 14-3-3ζ KO mice. Rather, our analysis identified significantly reduced levels of DAT in the absence of notable differences in RNA or protein levels of DA receptors D1-D5. Providing insight into the mechanisms by which 14-3-3ζ controls DAT stability, we found a physical association between 14-3-3ζ and DAT by co-immunoprecipitation. Taken together, our results identify a novel role for 14-3-3ζ in DA neurotransmission and provide support to the hyperdopaminergic basis of pathologies associated with schizophrenia and related disorders.

Topics: 14-3-3 Proteins; Amphetamine; Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Dopamine; Dopamine Agents; Dopamine Plasma Membrane Transport Proteins; Mice; Mice, Knockout; Motor Activity; Neostriatum; Schizophrenia; Signal Transduction; Synaptic Transmission

The glutamatergic hypothesis of schizophrenia proposes alterations of excitatory amino acid transporters (solute carrier family, SLCs) expression and cerebellar dysfunctions. The influence of the neuregulin-1 (NRG1) risk genotype or effects of antipsychotics on expression of EAATs are unknown.. We compared post-mortem samples from the cerebellar hemispheres and vermis of 10 schizophrenia patients with nine normal subjects by investigating gene expression of SLC1A3, SLC1A1 and SLC1A6 by in-situ hybridization. We further assessed the allelic composition regarding the polymorphism rs35753505 (SNP8NRG221533) near the NRG1 gene. To control for effects due to antipsychotic treatment, we chronically treated rats with the antipsychotics haloperidol or clozapine and assessed gene expression of SLCs.. Schizophrenia patients showed increased expression of SLC1A3 in the molecular layer of the vermis. Individuals carrying at least one C allele of rs35753505 (SNP8NRG221533) showed decreased expression of SLC1A6 in the molecular layer of both hemispheres, compared to individuals homozygous for the T allele. The animal model revealed suppression of SLC1A6 by clozapine.. Increased SLC1A3 expression indicates facilitated transport and may result in reduced glutamate neurotransmission. Decreased SLC1A6 expression in NRG1 risk variant may be an adaptive effect to restore glutamate signalling, but treatment effects cannot be excluded.

Topics: Aged; Alleles; Animals; Antipsychotic Agents; Cerebellum; Clozapine; Disease Models, Animal; Excitatory Amino Acid Transporter 1; Excitatory Amino Acid Transporter 3; Excitatory Amino Acid Transporter 4; Female; Gene Expression Regulation; Haloperidol; Humans; Male; Middle Aged; Neuregulin-1; Polymorphism, Single Nucleotide; Rats; Rats, Sprague-Dawley; Risk Factors; Schizophrenia

In schizophrenia patients, optimal treatment with antipsychotics requires weeks to months of sustained drug therapy. However, single administration of antipsychotic drugs can reverse schizophrenia-like behavioral alterations in rodent models of psychosis. This raises questions about the physiological relevance of such antipsychotic-like activity.. This study evaluates the effects of chronic treatment with clozapine on the cellular and behavioral responses induced by the hallucinogenic serotonin 5-HT(2A) receptor agonist lysergic acid diethylamide (LSD) as a mouse model of psychosis.. Mice were treated chronically (21 days) with 25 mg/kg/day clozapine. Experiments were conducted 1, 7, 14, and 21 days after the last clozapine administration. [(3)H]Ketanserin binding and 5-HT ( 2A ) mRNA expression were determined in mouse somatosensory cortex. Head-twitch behavior, expression of c-fos, which is induced by all 5-HT(2A) agonists, and expression of egr-1 and egr-2, which are LSD-like specific, were assayed.. Head-twitch response was decreased and [(3)H]ketanserin binding was downregulated in 1, 7, and 14 days after chronic clozapine. 5-HT ( 2A ) mRNA was reduced 1 day after chronic clozapine. Induction of c-fos, but not egr-1 and egr-2, was rescued 7 days after chronic clozapine. These effects were not observed after short treatment (2 days) with clozapine or chronic haloperidol (1 mg/kg/day).. Our findings provide a murine model of chronic atypical antipsychotic drug action and suggest downregulation of the 5-HT(2A) receptor as a potential mechanism involved in these persistent therapeutic-like effects.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Down-Regulation; Hallucinogens; Haloperidol; Lysergic Acid Diethylamide; Male; Mice; Mice, 129 Strain; Psychotic Disorders; Receptor, Serotonin, 5-HT2A; Serotonin 5-HT2 Receptor Agonists; Time Factors

Prior research has demonstrated that individuals with schizophrenia may exhibit lateral biases in attention and deficits in social behavior. The use of a noninvasive animal model of attentional impairments in schizophrenia and antipsychotic drugs can help elucidate the biological underpinnings of attentional processes and facilitate the study of novel therapeutics.. The purpose of this study was to compare the effects of three antipsychotic drugs on measures of lateral bias and social attention in healthy, unoperated female rats.. Female Long-Evans rats selected for a preexisting lateral bias in attention, a right behavioral orientation preference (BOP), were administered clozapine, haloperidol, sulpiride, or vehicle. Lateral bias in attention was assessed by determining which forelimb rats removed a nuisance stimulus from first. Social attention was examined by comparing the latency to remove nuisance stimuli in the presence of a social (inaccessible female rat) versus non-social (blinking clock) distractor.. All antipsychotic drugs eliminated right lateral bias in attention, while control animals retained their initial bias. Clozapine eliminated right lateral bias more rapidly than the other drugs. Animals receiving clozapine also selectively displayed increased attention to another rat.. The results suggest that the antipsychotic medication clozapine rapidly alters attentional bias and uniquely influences attention to a social stimulus. The right BOP paradigm is a useful animal model for comparing antipsychotic drug effects on lateralized attentional bias and attention to social stimuli.

Topics: Animals; Antipsychotic Agents; Attention; Behavior, Animal; Clozapine; Disease Models, Animal; Female; Functional Laterality; Haloperidol; Rats; Rats, Long-Evans; Social Behavior; Sulpiride

Evidence from epidemiological studies suggest that low levels of vitamin D during early life alter brain development and may increase the risk of various adverse health outcomes, including schizophrenia. The aim of this experiment was to examine the effect of developmental vitamin D (DVD) deficiency on attentional processing using the 5-choice serial reaction time task (5C-SRT) and the 5-choice continuous performance test (5C-CPT), which specifically assesses sustained attention and vigilance in rodents. DVD-deficient and control rats were exposed to a series of target and non-target trials within each operant testing session. A number of measures were recorded including hit, miss, false alarm and correct rejection, as well as premature and perseverative responses. Performance on 5C-CPT was also assessed after administration of the atypical antipsychotic, clozapine. The adult offspring of DVD-deficient rats had higher levels of impulsivity, as demonstrated by a significant increase in premature responses. On the 5C-SRT and target trials of the 5C-CPT, accuracy was not significantly affected by prenatal diet; however DVD-deficient rats made 50% fewer correct rejections compared to controls on non-target trials of the 5C-CPT. Thus, control rats were able to discriminate between target and non-target trials, whereas DVD-deficient rats were unable to make this discrimination. Clozapine reduced the occurrence of false alarms in DVD-deficient rats to a level comparable to control values. Taken together these data suggest DVD-deficient rats have increased impulsivity as well as a lack of inhibitory control, and these features may be informative in terms of modeling the cognitive deficits observed in schizophrenia.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Choice Behavior; Clozapine; Cognition Disorders; Disease Models, Animal; Female; Inhibition, Psychological; Male; Probability; Rats; Rats, Sprague-Dawley; Reaction Time; Sensitivity and Specificity; Time Factors; Vitamin D Deficiency

Prenatal immune system disturbances have been postulated to play an important role in pathogenesis of schizophrenia and related disorders. In the present study, we sought to answer the question whether behavioral changes in the neurodevelopmental model of schizophrenia in rats are accompanied by alterations in proliferative activity of splenocytes and pro- and anti-inflammatory cytokine levels. Furthermore, the effects of two antipsychotic drugs on these parameters were determined.. Lipopolysaccharide (LPS) was administered subcutaneously to pregnant dams at a dose of 1 mg/kg every second day from the 7(th) day of pregnancy till delivery. Age-dependent behavioral and immunological changes were studied when control and prenatally LPS-pretreated offspring male rats were 30 and 90 days old. Chlorpromazine (10 mg/kg ip) or clozapine (10 mg/kg ip) was administered chronically (21 days) after behavioral verification to 3 months old offspring males. Changes in sensorimotor gating (prepulse inhibition, PPI), mitogen-induced proliferative activity of splenocytes ([(3)H]-thymidine incorporation) and cytokine levels (ELISA) were measured.. Prenatally LPS-pretreated rats showed PPI deficit only at 90 but not at 30 days of age, whereas an enhancement of mitogen-stimulated proliferative activity of splenocytes was observed in both time points. Additionally, the level of proinflammatory cytokines (IL-1β, IL-2, IL-6, TNF-α) in prenatally LPS-pretreated rats was enhanced when they were 30 days old and remained elevated in 90 days old offspring. No changes in IL-10 level were observed. Chronic administration of chlorpromazine or clozapine reduced the deficit in PPI deficit in prenatally LPS-treated rats. In the used model, chlorpromazine normalized both T and B lymphocyte proliferation, whereas clozapine B lymphocyte activity only. Moreover, both antipsychotics modulated the enhanced levels of IL-1β, IL-2 and TNF-α in the offspring of LPS-treated mothers.. This study indicates that in LPS-evoked model of schizophrenia, peripheral immunological changes are long-lasting and precede behavioral deficit. The disturbances in T cell-mediated immunity as well as cytokine production were attenuated by antipsychotic drug administration.

Topics: Age Factors; Aging; Animals; Antipsychotic Agents; Behavior, Animal; Cell Proliferation; Cells, Cultured; Chlorpromazine; Clozapine; Cytokines; Disease Models, Animal; Disease Progression; Drug Administration Schedule; Enzyme-Linked Immunosorbent Assay; Female; Inflammation Mediators; Injections, Subcutaneous; Lipopolysaccharides; Lymphocyte Activation; Male; Maternal Exposure; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Wistar; Reflex, Startle; Schizophrenia; Schizophrenic Psychology; Sensory Gating; Spleen; T-Lymphocytes; Time Factors

N-Methyl-D-aspartate (NMDA) receptor (NMDAR) hypofunction has been postulated to contribute to the cognitive deficit of schizophrenia. In this study, we examined the effect of lurasidone (Latuda; Dainippon Sumitomo Pharma Co. Ltd., Tokyo, Japan), a newly approved atypical antipsychotic drug (APD), on NMDAR synaptic function in rat frontal cortical pyramidal neurons. In vivo administration of lurasidone produced a significant and selective enhancement of NMDAR-mediated synaptic responses and surface expression of NR2A and NR2B subunits. Lurasidone has high affinity for serotonin 5-HT(1A), 5-HT(2A), and 5-HT(7) receptors and dopamine D(2) receptors. In vivo administration of the 5-HT(7) receptor antagonist (2R)-1-[(3-hydroxyphenyl)sulfonyl]-2 -(2-(4-methyl-1-piperidinyl)ethyl)pyrrolidine (SB-269970) mimicked the enhancing effect of lurasidone on NMDAR responses, whereas the D(2) receptor antagonist haloperidol failed to do so. Previous studies have found that short-term administration of lurasidone reverses the cognitive impairment induced by subchronic administration of phencyclidine (PCP), an NMDAR noncompetitive antagonist. In this study, we found that lurasidone, as well as the prototypical atypical APD clozapine, restored NMDAR-mediated synaptic responses to normal levels in the PCP model of schizophrenia. These results suggest that NMDAR is the potential key molecular target of lurasidone, possibility via antagonizing 5-HT(7) receptors, which is consistent with evidence that 5-HT(7) receptor antagonism contributes to cognitive enhancement by atypical APDs in patients with schizophrenia.

Topics: Animals; Antipsychotic Agents; Clozapine; Cognition Disorders; Disease Models, Animal; Isoindoles; Lurasidone Hydrochloride; Rats; Receptor, Serotonin, 5-HT2A; Receptors, N-Methyl-D-Aspartate; Schizophrenia; Synaptic Transmission; Thiazoles

Long-term treatment with haloperidol is associated with a number of extrapyramidal side effects. This limitation presents a marked therapeutic challenge. The present method (21 days administration of haloperidol, 5 mg/kg, i.p.) has been established to gain deeper insight into the molecular etiology (inflammation and apoptosis) of haloperidol-induced cellular death. In the present model, besides the corresponding increase in the vacuous chewing movements (VCMs), enhanced oxidative stress, there was a significant increase in cellular markers of inflammation and apoptotic protein (caspase-3), leading to cellular death. We also suggest that this model will be effective in preclinical testing of new chemical entities for the treatment of haloperidol induced tardive dyskinesia and related symptoms.

Topics: Animals; Antipsychotic Agents; Apoptosis; Behavior, Animal; Caspase 3; Clozapine; Disease Models, Animal; Dyskinesia, Drug-Induced; Haloperidol; Humans; Male; Movement Disorders; Pregnatrienes; Rats; Rats, Wistar

The abnormal synchronisation of neural networks may underlie some of the deficits observed in schizophrenia. Abnormal synchronisation can be induced in animal models. We investigated whether acute clozapine treatment might function therapeutically by ameliorating the deficit in theta frequency coherence between the prefrontal cortex and the hippocampus that is induced in rats exposed to maternal immune activation (MIA)--a risk-factor for schizophrenia. Clozapine treatment increased synchrony levels to that of control animals in a dose-dependent manner. Clozapine's effect on synchrony may in part be mediated through increases in local synchrony that occurred in prefrontal cortex but not hippocampus.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Electroencephalography Phase Synchronization; Exploratory Behavior; Female; Hippocampus; Male; Poly I-C; Prefrontal Cortex; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Sprague-Dawley; Rest; Schizophrenia

Glycine N-methyltransferase (GNMT) affects cellular methylation capacity through regulating the ratio between S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH). The product of its enzymatic reaction-sarcosine has antipsychotic effect in patients with schizophrenia. In this study, through RT-PCR and immunohistochemical staining, we demonstrated that GNMT expressed in various neurons located in the cerebral cortex, hippocampus, substantia nigra and cerebellum. Compared to the wild-type mice, Gnmt-/- mice had significantly lower level of sarcosine in the cerebral cortex. Real-time PCR identified genes involved in the methionine metabolism (Dnmt1 and Dnmt3a), ErbB (Nrg1 and ErbB4) and mTOR (Akt2, S6, S6k1 and S6k2) signaling pathways were dysregulated significantly in the cortex of Gnmt-/- mice. Acoustic startle reflex test demonstrated that Gnmt-/- mice had significantly lower level of prepulse inhibition and the deficit was ameliorated through clozapine or sarcosine treatment. Furthermore, liver-specific-human-GNMT transgenic with Gnmt-/- (Tg-GNMT/Gnmt-/-) mice were used to rule out that the phenotype was due to abnormal liver function. In summary, the neuropsychological abnormalities found in Gnmt-/- mice may represent an endophenotype of schizophrenia. GNMT plays an important role in maintaining normal physiological function of brain and Tg-GNMT/Gnmt-/- mice are useful models for development of therapeutics for patients with schizophrenia.

Topics: Animals; Antipsychotic Agents; Clozapine; Crosses, Genetic; Disease Models, Animal; Gene Expression Regulation; Glycine N-Methyltransferase; Humans; Male; Metencephalon; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Nerve Tissue Proteins; Neurons; Organ Specificity; RNA, Messenger; Sarcosine; Schizophrenia; Signal Transduction

This study combined two neurodevelopmental manipulations, neonatal MK-801 treatment and isolation rearing, to produce a 'two-hit' model and determine whether two hits induce a more robust behavioural phenotype of an animal model of aspects of schizophrenia compared with individual manipulations alone. The effect of clozapine was also assessed. Male Sprague-Dawley rats received 0.2 mg/kg MK-801 or saline intraperitoneally (i.p.) once daily on postnatal days (PNDs) 7-10 and were assigned to group or isolation rearing at weaning (PND 21). From PND 77, they received a vehicle or 5 mg/kg clozapine (i.p.) treatment regimen and were subjected to three prepulse inhibition (PPI) tests, a locomotor activity assessment and a novel object recognition task. MK-801-treated rats reared in isolation displayed robust PPI disruptions which were consistently manifested in all three tests. PPI deficits were also detected in saline-treated rats reared in isolation but not in all tests. Only the two-hit rats demonstrated hyperlocomotion and impaired object recognition memory. Clozapine restored PPI anomalies in the two-hit rats. The two-hit model showed greater psychotic-like effects than either neonatal MK-801 or isolation rearing alone. The preliminary predictive validity shown with clozapine suggests this model may be useful for predicting the efficacy of putative antipsychotics.

Topics: Akathisia, Drug-Induced; Animals; Animals, Newborn; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Exploratory Behavior; Injections, Intraperitoneal; Male; Maternal Deprivation; Memory Disorders; Neural Inhibition; Neurotoxicity Syndromes; Random Allocation; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Schizophrenia

Recently, a novel paradigm has been designed to assess social investigative behaviour in pairs of Sprague-Dawley rats, which involves physical separation whilst ensuring they are able to maintain contact through other social cues. We have modified this set-up in order to assess not just social behaviour but also locomotor activity of the rats. Results showed that the MK-801- (0.3 mg/kg) treated rats displayed reduced social investigative behaviour, hyperactivity as well as reduced attention span. Pretreatment with the phytocannabinoid cannabidiol (3 mg/kg) not only normalised social investigative behaviour but increased it beyond control levels. Pretreatment with clozapine (1, 3 mg/kg) also normalised social investigative behaviour. Both cannabidiol and clozapine inhibited MK-801-induced hyperactivity. However, there were no effects of pretreatment on impairments to attention span. Our findings reinforce several aspects of the validity of the MK-801-induced model of social withdrawal and hyperactivity and also support the use of this novel set-up for further investigations to assess the antipsychotic potential of novel compounds.

Topics: Animals; Antipsychotic Agents; Attention; Attention Deficit Disorder with Hyperactivity; Behavior, Animal; Cannabidiol; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Male; Motor Activity; Psychomotor Agitation; Psychotropic Drugs; Rats; Rats, Sprague-Dawley; Schizophrenia; Social Behavior; Social Behavior Disorders

Schizophrenia is a chronic and highly complex psychiatric disorder characterised by cognitive dysfunctions, negative and positive symptoms. The major challenge in schizophrenia research is lack of suitable animal models that mimic the core behavioural aspects and symptoms of this devastating psychiatric disorder. In this study, we used classical and atypical antipsychotic drugs to examine the predictive validity of ketamine-enhanced immobility in forced swim test (FST) as a possible animal model for the negative symptoms of schizophrenia. We also evaluated the effects of a selective serotonin reuptake inhibitor (SSRI) on the ketamine-enhanced immobility in FST. Repeated administration of a subanaesthetic dose of ketamine (30 mg kg(-1), i.p., daily for 5 days) enhanced the duration of immobility in FST 24 h after the final injection. The effect, which persisted for at least 21 days after withdrawal of the drug, was neither observed by single treatment with ketamine (30 mg kg(-1) i.p.) nor repeated treatment with amphetamine (1 and 2 mg kg(-1) i.p., daily for 5 days). The enhancing effects of ketamine (30 mg kg(-1) day(-1) i.p.) on the duration of immobility in the FST were attenuated by clozapine (1, 5 and 10 mg kg(-1) i.p.), risperidone (0.25 and 0.5 mg kg(-1) i.p.) and paroxetine (1 and 5 mg kg(-1) i.p.). Haloperidol (0.25 and 0.50 mg kg(-1) day(-1) i.p.) failed to attenuate the ketamine-enhanced immobility in the FST. The repeated ketamine administration neither affects locomotor activity nor motor coordination in rats under the same treatment conditions with the FST, suggesting that the effects of ketamine on the duration of immobility in this study was neither due to motor dysfunction nor peripheral neuromuscular blockade. Our results suggest that repeated treatment with subanaesthetic doses of ketamine enhance the duration of immobility in FST, which might be a useful animal model for the negative symptoms (particularly the depressive features) of schizophrenia.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Female; Haloperidol; Immobility Response, Tonic; Ketamine; Male; Motor Activity; Rats; Rats, Wistar; Reproducibility of Results; Risperidone; Schizophrenia; Swimming

We compared the effects of subchronic clozapine and haloperidol administration on the expression of SNAP-25 and synaptophysin in an animal model of schizophrenia based on the glutamatergic hypothesis. Mice were first treated with a non-competitive NMDA antagonist MK-801 (0.3 mg/kg/day) or saline for 5 days, and then clozapine (5 mg/kg/day), haloperidol (1 mg/kg/day) or saline was administered for two weeks. The locomotion test, as a behavioral model of the positive symptoms of schizophrenia, was applied after MK-801/saline administration on day 6 for acute effects and after antipsychotic/saline administration on day 19 for enduring effects on mice activity. Memory function was assessed by the Novel Object Recognition (NOR) test, one day after the last day of antipsychotic/saline administration (day 20). Western Blotting technique was used to determine SNAP-25 and synaptophysin expressions in the hippocampus and frontal cortex. Both antipsychotics reversed the enhanced locomotion effects of MK-801. MK-801 and haloperidol decreased recognition memory performance. On the other hand, clozapine did not compromise memory. It also did not reverse the negative effects of MK-801 on memory performance. MK-801 did not change SNAP-25 and synaptophysin expressions in the hippocampus and frontal cortex. Clozapine increased hippocampal SNAP-25, decreased hippocampal synaptophysin expression, whereas frontal SNAP-25 and synaptophysin expressions remained unchanged. Haloperidol had no effects on levels of SNAP-25 and synaptophysin in the frontal cortex and hippocampus. These findings support the idea that the differential effects of clozapine might be related to its plastic effects and synaptic reorganization of the hippocampus.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Frontal Lobe; Haloperidol; Hippocampus; Male; Mice; Motor Activity; Presynaptic Terminals; Recognition, Psychology; Schizophrenia; Synaptophysin; Synaptosomal-Associated Protein 25

The immediate-early gene early growth response 3 (Egr3) is associated with schizophrenia and expressed at reduced levels in postmortem patients' brains. We have previously reported that Egr3-deficient (Egr3(-/-)) mice display reduced sensitivity to the sedating effects of clozapine compared with wild-type (WT) littermates, paralleling the heightened tolerance of schizophrenia patients to antipsychotic side effects. In this study, we have used a pharmacological dissection approach to identify a neurotransmitter receptor defect in Egr3(-/-) mice that may mediate their resistance to the locomotor suppressive effects of clozapine. We report that this response is specific to second-generation antipsychotic agents (SGAs), as first-generation medications suppress the locomotor activity of Egr3(-/-) and WT mice to a similar degree. Further, in contrast to the leading theory that sedation by clozapine results from anti-histaminergic effects, we show that H1 histamine receptors are not responsible for this effect in C57BL/6 mice. Instead, selective serotonin 2A receptor (5HT(2A)R) antagonists ketanserin and MDL-11939 replicate the effect of SGAs, repressing the activity in WT mice at a dosage that fails to suppress the activity of Egr3(-/-) mice. Radioligand binding revealed nearly 70% reduction in 5HT(2A)R expression in the prefrontal cortex of Egr3(-/-) mice compared with controls. Egr3(-/-) mice also exhibit a decreased head-twitch response to 5HT(2A)R agonist 1-(2,5-dimethoxy 4-iodophenyl)-2-amino propane (DOI). These findings provide a mechanism to explain the reduced sensitivity of Egr3(-/-) mice to the locomotor suppressive effects of SGAs, and suggest that 5HT(2A)Rs may also contribute to the sedating properties of these medications in humans. Moreover, as the deficit in cortical 5HT(2A)R in Egr3(-/-) mice aligns with numerous studies reporting decreased 5HT(2A)R levels in the brains of schizophrenia patients, and the gene encoding the 5HT(2A)R is itself a leading schizophrenia candidate gene, these findings suggest a potential mechanism by which putative dysfunction in EGR3 in humans may influence risk for schizophrenia.

Topics: Animals; Clozapine; Disease Models, Animal; Early Growth Response Protein 3; Humans; Hypnotics and Sedatives; Ketanserin; Male; Mice; Mice, Transgenic; Motor Activity; Piperidines; Receptor, Serotonin, 5-HT2A; Schizophrenia; Serotonin 5-HT2 Receptor Agonists; Serotonin Antagonists

Clozapine has markedly superior clinical properties compared to other antipsychotic drugs but the side effects of agranulocytosis, weight gain and diabetes limit its use. The reason why clozapine is more effective is not well understood. We studied messenger RNA (mRNA) gene expression in the mouse brain to identify pathways changed by clozapine compared to those changed by haloperidol so that we could identify which changes were specific to clozapine. Data interpretation was performed using an over-representation analysis (ORA) of gene ontology (GO), pathways and gene-by-gene differences. Clozapine significantly changed gene expression in pathways related to neuronal growth and differentiation to a greater extent than haloperidol; including the microtubule-associated protein kinase (MAPK) signalling and GO terms related to axonogenesis and neuroblast proliferation. Several genes implicated genetically or functionally in schizophrenia such as frizzled homolog 3 (FZD3), U2AF homology motif kinase 1 (UHMK1), pericentriolar material 1 (PCM1) and brain-derived neurotrophic factor (BDNF) were changed by clozapine but not by haloperidol. Furthermore, when compared to untreated controls clozapine specifically regulated transcripts related to the glutamate system, microtubule function, presynaptic proteins and pathways associated with synaptic transmission such as clathrin cage assembly. Compared to untreated controls haloperidol modulated expression of neurotoxic and apoptotic responses such as NF-kappa B and caspase pathways, whilst clozapine did not. Pathways involving lipid and carbohydrate metabolism and appetite regulation were also more affected by clozapine than by haloperidol.

Topics: Animals; Antipsychotic Agents; Brain; Cell Cycle Proteins; Clozapine; Disease Models, Animal; Gene Expression Profiling; Gene Expression Regulation; Haloperidol; Male; Mice; Mice, Inbred C57BL; Microtubule Proteins; Nerve Tissue Proteins; Neurons; Oligonucleotide Array Sequence Analysis; Organ Specificity; Pilot Projects; RNA, Messenger; Schizophrenia

In this paper, we report the discovery and the synthesis of novel, potential antipsychotic piperidine-2,6-dione derivatives combining potent dopamine D(2) , D(3) and serotonin 5-HT(1A) , 5-HT(2A) , 5-HT(2C) receptor properties. We describe the structure-activity relationships that led us to the promising derivative: 1-(4-(4-(6-fluorobenzo[d]isoxazol-3-yl)piperidin-1-yl)butyl)-4-(4-chlorophenyl)-piperidine-2,6-dione 5. The unique pharmacological features of compound 5 are a high affinity for dopamine D(2) , D(3) and serotonin 5-HT(1A) , 5-HT(2A) , 5-HT(2C) receptors, together with a low affinity for the H(1) receptor (to reduce the risk of obesity under chronic treatment). In a behavioral model predictive of positive symptoms, compound 5 inhibited apomorphine-induced climbing behavior and MK-801-induced hyperactivity with no extrapyramidal symptoms liability in mice. In particular, compound 5 was more potent than clozapine.

Topics: Animals; Antipsychotic Agents; Apomorphine; Behavior, Animal; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Mice; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, Dopamine; Receptors, Histamine H1; Receptors, Serotonin; Structure-Activity Relationship

Topics: Analysis of Variance; Animals; Antiparkinson Agents; Antipsychotic Agents; Apomorphine; Aquaporin 4; Clozapine; Corpus Striatum; Disease Models, Animal; Glial Fibrillary Acidic Protein; Haloperidol; Hippocampus; Male; Mastication; Mice; Mice, Knockout; Motor Activity; Movement Disorders

Lack of appropriate animal models simulating core behavioural aspects of human psychosis is a major limitation in schizophrenia research. The use of drugs, that is believed to act through N-methyl d-aspartate receptor, has been demonstrated to mimic relatively broader range of behavioural symptoms in putative animal models. Our goal in this study has been to further evaluate one such drug, ketamine in mice and characterize some selective behavioural phenotypes associated with the drug dosage, treatment period and withdrawal effects to extend the understanding of this model. Our results indicate that acute treatment of ketamine (100 mg/kg, i.p.) induced hyperlocomotory response and reduced the 'transfer-latency time' in passive avoidance test but did not have any effect in the forced swim test (negative symptoms). In contrast, chronic administration of ketamine not only produced significant 'hyperactivity' response but also enhanced the immobility period in animals during the forced swim test and reduced the latency period in the passive avoidance test. Further, these behavioural alterations persisted at least for 10 days after the withdrawal of ketamine treatment. These observations were substantiated by using standard typical and atypical antipsychotic drugs, haloperidol (0.25 mg/kg, i.p.), clozapine (10 mg/kg, i.p.) and risperidone (0.025 mg/kg, i.p.). Therefore, the present study suggests that the chronic treatment with ketamine has the potential of exhibiting changes in broader range of behavioural domains than the acute treatment. Hence, animals chronically treated with ketamine might serve as a useful tool to study the underlying pathogenic mechanisms associated with some symptoms in schizophrenia and other psychiatric disorders.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Avoidance Learning; Behavior, Animal; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Haloperidol; Ketamine; Male; Mice; Motor Activity; Psychotic Disorders; Random Allocation; Risperidone; Schizophrenia; Substance Withdrawal Syndrome; Swimming

Cognitive deficits are a core feature of schizophrenia that respond minimally to existing drugs. PCP is commonly used to model schizophrenia-like deficits preclinically although different dosing protocols may affect different domains. Here we characterise the acute, and chronic intermittent effects of PCP in the 5-choice serial reaction time task (5-CSRTT) in rats, and assess the effects of clozapine. In a novel approach, we also assess the effects of increased inhibitory load and conduct clinically relevant signal detection analysis (SDA).. The effects of acute and repeated PCP (2.58 mg/kg) treatment on attentional processes and inhibitory control were assessed during and following the chronic treatment regime in the presence or absence of chronic clozapine (20 mg/kg/day).. Thirty minutes post-PCP injection, there was an increase in anticipatory responding which disappeared after 24 h. Although, acute PCP did not change accuracy of responding or processing speed, repeated PCP revealed delayed deficits in cognitive processing speed which were partly ameliorated by clozapine. Extended inter-trial intervals increased premature responding, while SDA revealed that clozapine modified persistent PCP-induced deficits in lnBeta (a composite measure of risk taking versus caution).. Acute NMDA receptor antagonism impairs inhibitory control, whereas repeated treatment produces delayed deficits in cognitive processing speed. The ability of clozapine partially to restore persistent PCP-induced deficits in processing speed and in lnBeta is consistent with clinical findings. This suggests that the enduring effects of repeated PCP treatment, combined with SDA, offers a useful, translational, approach to evaluate novel cognitive enhancers in the 5-CSRTT.

Topics: Animals; Antipsychotic Agents; Attention; Choice Behavior; Clozapine; Cognition Disorders; Disease Models, Animal; Drug Administration Schedule; GABA Antagonists; Male; Phencyclidine; Rats; Rats, Long-Evans; Reaction Time; Receptors, N-Methyl-D-Aspartate; Signal Detection, Psychological; Time Factors

Adverse events early in life, including maternal separation and social isolation, profoundly affect brain development and adult behaviour and may contribute to the occurrence of psychiatric disorders such as schizophrenia and mood disorders in genetically predisposed individuals. The molecular mechanisms underlying these environmentally induced developmental adaptations are unclear and best evaluated in animal paradigms with translational salience. In this study, we examined the effects in mice of maternal separation and/or social isolation for 6 h/d between postnatal days 15 and 21 on performance during adulthood in the open-field, social interaction, elevated plus-maze, forced swimming, Y-maze, novel object recognition, conditioned fear-learning, prepulse inhibition, and locomotor activity tests, to investigate whether this animal model could show the phenotypes for schizophrenia and mood disorders. The stress of maternal separation and isolation led to adult behavioural deficits, activation of the hypothalamic-pituitary-adrenal axis, and decreases in the levels of norepinephrine and dopamine in the frontal cortex and metabolites of dopamine and serotonin in the amygdala, showing the involvement of endocrine and neuronal risk in behavioural deficits. The results suggest that the frontal cortex and amygdala undergo structural remodelling induced by the stress of maternal separation and isolation, which alters behavioural and physiological responses in adulthood, including anxiety, memory and other cognitive processes. Further, social isolation enhanced the behavioural dysfunctions induced by maternal separation. These findings indicate that maternal separation and social isolation early in life can lead to long-lasting abnormal behaviour and pathophysiological impairments including schizophrenia and mood disorders.

Topics: Animals; Antipsychotic Agents; Anxiety; Behavior, Animal; Clozapine; Disease Models, Animal; Environment; Fear; Hypothalamo-Hypophyseal System; Male; Maternal Deprivation; Maze Learning; Mental Disorders; Mice; Mice, Inbred C57BL; Motor Activity; Neurotransmitter Agents; Pituitary-Adrenal System; Social Isolation; Swimming

Marijuana (Cannabis sativa) is one of the most widely used illicit drugs in the world. Its use is associated with impairments in cognitive function. We previously reported that Δ(9)-tetrahydrocannabinol (Δ(9)-THC), the primary psychoactive component of marijuana, impaired spatial working memory in the radial maze task when injected intracortically (IC) into the medial prefrontal cortex (mPFC) of rats. Here, we used this paradigm to evaluate the involvement of prefrontal dopamine receptors in working memory disruption induced by Δ(9)-THC. Intracortical pre-treatment of animals with either the D(1)- or D(2)-like dopamine receptor antagonists SCH 23390 or clozapine, respectively, significantly reduced the number of errors rats made in the radial maze following treatment with Δ(9)-THC also administered intracortically. These results were obtained in the absence of locomotor impairment, as evidenced by the time spent in each arm a rat visited. Our findings suggest that prefrontal dopamine receptors are involved in Δ(9)-THC-induced disruption of spatial working memory. This interaction between the cannabinoid system and dopamine release in the PFC contributes to new directions in research and to treatments for cognitive dysfunctions associated with drug abuse and dependence.

Topics: Animals; Benzazepines; Clozapine; Disease Models, Animal; Dopamine Antagonists; Dronabinol; Male; Maze Learning; Memory Disorders; Prefrontal Cortex; Psychotropic Drugs; Rats; Rats, Wistar

Cannabidiol is a non-psychoactive phytocannabinoid which, based on several previous preclinical and clinical reports, is purported to have antipsychotic potential. The purpose of this investigation was to further investigate if these effects would be seen using an MK-801-induced rat model of aspects of schizophrenia. MK-801 is an NMDA receptor-antagonist known to produce hyperactivity, deficits in prepulse inhibition and social withdrawal, behaviours which correlate well with some of the positive, cognitive and negative symptoms of schizophrenia. Following a 4-day acclimatisation to the holding room, rats were acclimatised to startle chambers on day 5 and their prepulse inhibition (PPI) determined on day 6 following treatment with cannabidiol or vehicle and MK-801 or vehicle. On day 9, rats were acclimatised to the social interaction testing arena and on day 10, were tested for social interaction and locomotor activity following the same treatments. Cannabidiol treatment alone disrupted PPI and produced hyperactivity but had no effect on social behaviour. Cannabidiol had no effect on MK-801-induced disruption of PPI or hyperactivity but showed potential towards inhibiting MK-801-induced social withdrawal. As a comparator, we also tested the effect of the atypical antipsychotic clozapine which only partially reversed MK-801-induced disruption of PPI but was able to reverse MK-801-induced hyperactivity and social withdrawal. In conclusion, cannabidiol showed both propsychotic activity and partial antipsychotic activity in an MK-801-induced model of aspects of schizophrenia. Further behavioural studies would be required using a range of species, strains, animal models and testing paradigms to conclusively establish the antipsychotic potential of cannabidiol.

Topics: Animals; Antipsychotic Agents; Cannabidiol; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Drug Interactions; Inhibition, Psychological; Interpersonal Relations; Male; Motor Activity; Rats; Rats, Sprague-Dawley; Reflex, Startle; Schizophrenia

Patients with schizophrenia have been shown to display decreased sensitivity to pain, which can severely compound the impact of injuries and illnesses. Alterations in the sensory and affective systems of pain processing have been proposed as mechanisms, but the unique contribution of each of these systems has not been elucidated. The aim of this study was to investigate these two components of pain using the NMDA receptor antagonist, phencyclidine (PCP), an established animal model of schizophrenia. Animals underwent L5 spinal nerve ligation surgery in order to provoke a condition of ongoing pain responding, followed by treatment with 2.58 mg/kg of PCP, or saline, and 20 mg/kg of the atypical antipsychotic clozapine, or vehicle, in a block design. Responses to mechanical stimuli were assessed to determine changes in sensory processing, and affective pain processing was examined with the place escape avoidance paradigm. The results showed animals receiving PCP exhibited decreased sensitivity to mechanical stimulation and unaltered behavior in the avoidance paradigm. These findings corroborate and strengthen the human literature investigating schizophrenia and alterations in pain perception. More importantly, the differential findings between the tests of sensory and affective pain processing provide a novel means of understanding schizophrenia-related pain insensitivity.

Topics: Animals; Antipsychotic Agents; Avoidance Learning; Clozapine; Disease Models, Animal; Escape Reaction; Excitatory Amino Acid Antagonists; Ligation; Male; Neuralgia; Pain Perception; Phencyclidine; Physical Stimulation; Rats; Rats, Long-Evans; Receptors, N-Methyl-D-Aspartate; Schizophrenia; Spinal Nerves; Stress, Mechanical

Deficits in an operational measure of sensorimotor gating - the prepulse inhibition of startle (PPI) - are presented in psychiatric disorders such as schizophrenia, bipolar disorder, and attention deficit/hyperactivity disorder (ADHD). Some previous studies showed that the spontaneously hypertensive rats (SHR) present PPI deficit. Although SHR is suggested as an animal model to study ADHD, we have suggested that the behavioral phenotype of this strain mimics some aspects of schizophrenia. The aim of this study was to characterize the PPI response in SHR. Pharmacological characterization consisted in the evaluation of the effects of the following drugs administered to adult Wistar rats (WR) and SHR previously to the PPI test: amphetamine (used for ADHD and also a psychotomimetic drug), haloperidol and clozapine (antipsychotic drugs), metoclopramide (dopamine antagonist without antipsychotic properties) and carbamazepine (mood stabilizer). Our results showed that SHR presented reduced PPI. This deficit was similar to that induced by amphetamine in WR. Only the atypical antipsychotic clozapine improved the PPI deficit observed in SHR. These findings reinforce the SHR strain as an animal model to study several aspects of schizophrenia, including the abnormalities in sensorimotor gating associated with this disease.

Topics: Acoustic Stimulation; Amphetamine; Animals; Antimanic Agents; Antipsychotic Agents; Carbamazepine; Clozapine; Disease Models, Animal; Dopamine Antagonists; Dopamine Uptake Inhibitors; Male; Metoclopramide; Rats; Rats, Inbred SHR; Rats, Wistar; Reflex, Startle; Schizophrenia; Sensory Gating

Stem cell-based regenerative therapy is considered a promising cellular therapeutic approach for the patients with incurable brain diseases. Mesenchymal stem cells (MSCs) represent an attractive cell source for regenerative medicine strategies for the treatment of the diseased brain. Previous studies have shown that these cells improve behavioral deficits in animal models of neurological disorders such as Parkinson's and Huntington's diseases. In the current study, we examined the capability of intracerebral human MSCs transplantation (medial pre-frontal cortex) to prevent the social impairment displayed by mice after withdrawal from daily phencyclidine (PCP) administration (10 mg kg(-1) daily for 14 days). Our results show that MSCs transplantation significantly prevented the PCP-induced social deficit, as assessed by the social preference test. In contrast, the PCP-induced social impairment was not modified by daily clozapine treatment. Tissue analysis revealed that the human MSCs survived in the mouse brain throughout the course of the experiment (23 days). Significantly increased cortical brain-derived neurotrophic factor levels were observed in the MSCs-treated group as compared with sham-operated controls. Furthermore, western blot analysis revealed that the ratio of phosphorylated Akt to Akt was significantly elevated in the MSCs-treated mice compared with the sham controls. Our results demonstrate that intracerebral transplantation of MSCs is beneficial in attenuating the social deficits induced by sub-chronic PCP administration. We suggest a novel therapeutic approach for the treatment of schizophrenia-like negative symptoms in animal models of the disorder.

Topics: Adult Stem Cells; Animals; Behavior, Animal; Brain-Derived Neurotrophic Factor; Clozapine; Disease Models, Animal; Humans; Mesenchymal Stem Cell Transplantation; Mice; Phencyclidine; Prefrontal Cortex; Social Behavior; Up-Regulation

Current pharmacotherapy of schizophrenia remains unsatisfactory with little hope for complete functional restoration in patients once the disease has developed. A preventive approach based on intervention in the prodromal stage of the disease aiming to preserve functional integrity by halting the progress of the disease is therefore extremely attractive. Here, we investigated the effects of preventive antipsychotic or antidepressant drug treatment in a well-established neurodevelopmental mouse model of multiple schizophrenia-related abnormalities. Pregnant mice on gestation day 9 were exposed to the viral mimic polyriboinosinic-polyribocytidylic acid (2 mg/kg, intravenously) or corresponding vehicle treatment, and the resulting offspring from both prenatal treatment conditions were subjected to chronic antipsychotic (haloperidol or clozapine), antidepressant (fluoxetine), or placebo treatment during the periadolescent stage of development. The effects of the preventive pharmacotherapy on behavioral and pharmacological functions were then investigated in adulthood using paradigms relevant to schizophrenia, namely prepulse inhibition, latent inhibition, and sensitivity to psychostimulant drugs. We show that periadolescent treatment with the reference antipsychotic and antidepressant drugs can successfully block the emergence of multiple psychosis-related behavioral and pharmacological abnormalities in subjects predisposed to adult brain pathology by exposure to prenatal immune challenge. At the same time, however, our study reveals numerous negative influences of the early pharmacological intervention on normal behavioral development in control subjects. Hence, even though preventive pharmacotherapy may be beneficial in individuals with predisposition to psychosis-related brain dysfunctions, chronic antipsychotic or antidepressant drug treatment in false-positive subjects is associated with substantial risk for long-term behavioral disturbances in adulthood.

Topics: Age Factors; Amphetamine; Animals; Animals, Newborn; Antidepressive Agents, Second-Generation; Antipsychotic Agents; Brain; Central Nervous System Stimulants; Clozapine; Disease Models, Animal; Female; Haloperidol; Male; Mice; Mice, Inbred C57BL; Motor Activity; Neural Inhibition; Polynucleotides; Pregnancy; Prenatal Exposure Delayed Effects; Schizophrenia; Schizophrenic Psychology; Sensory Gating

Schizophrenia has been initially associated with dysfunction in dopamine neurotransmission. However, the observation that antagonists of the glutamate N-methyl-D-aspartate (NMDA) receptor produce schizophrenic-like symptoms in humans has led to the idea of a dysfunctioning of the glutamatergic system via its NMDA receptor. As a result, there is a growing interest in the development of pharmacological agents with potential antipsychotic properties that enhance the activity of the glutamatergic system via a modulation of the NMDA receptor. Among them are glycine transporter-1 (GlyT1) inhibitors such as SSR103800, which indirectly enhance NMDA receptor function by increasing the glycine (a co-agonist for the NMDA receptor) levels in the synapse. This study aimed at investigating the potential antipsychotic-like properties of SSR103800, with a particular focus on models of hyperactivity, involving either drug challenge (ie, amphetamine and MK-801) or transgenic mice (ie, NMDA Nr1(neo-/-) and DAT(-/-)). Results showed that SSR103800 (10-30 mg/kg p.o.) blocked hyperactivity induced by the non-competitive NMDA receptor antagonist, MK-801 and partially reversed spontaneous hyperactivity of NMDA Nr1(neo-/-) mice. In contrast, SSR103800 failed to affect hyperactivity induced by amphetamine or naturally observed in dopamine transporter (DAT(-/-)) knockout mice (10-30 mg/kg p.o.). Importantly, both classical (haloperidol) and atypical (olanzapine, clozapine and aripiprazole) antipsychotics were effective in all these models of hyperactivity. However, unlike these latter, SSR103800 did not produce catalepsy (retention on the bar test) up to 30 mg/kg p.o. Together these findings show that the GlyT1 inhibitor, SSR103800, produces antipsychotic-like effects, which differ from those observed with compounds primarily targeting the dopaminergic system, and has a reduced side-effect potential as compared with these latter drugs.

Topics: Amphetamine; Analysis of Variance; Animals; Antipsychotic Agents; Aripiprazole; Catalepsy; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Dopamine Plasma Membrane Transport Proteins; Glycine Plasma Membrane Transport Proteins; Hyperkinesis; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Activity; Piperazines; Quinolones; Receptors, N-Methyl-D-Aspartate

Glutamate and dopamine disturbances are implicated in frontal cortical dysfunction in schizophrenia. Little, however, is known about the nature of dopamine D(1) and N-methyl-D-aspartate (NMDA) receptor interactions in the illness, nor of the extent of their co-involvement in antipsychotic drug response. It is well known that early life adversity may pre-date the development of schizophrenia. Using a neurodevelopmental model of schizophrenia, namely post weaning social isolation rearing (SIR), we studied the effect of SIR (post natal day 21-61) on frontal cortical NMDA and D(1) receptor binding characteristics with/without chronic haloperidol (0.1 mg/kg/day i.p.) or clozapine (5 mg/kg/day i.p.) treatment, undertaken from post-natal day 50-60. SIR increased frontal cortical NMDA-density, with decreased affinity (decreased pK(D)), but reduced D(1) receptor density (without effects on pK(D)). In socially reared animals, clozapine but not haloperidol increased NMDA receptor density without effects on pK(D.) Neither drug markedly affected D(1) receptor density, although clozapine increased D(1) affinity. Increased NMDA density in SIR animals was unaffected by haloperidol, but further increased by clozapine. However, SIR-associated decrease in NMDA affinity remained unaltered despite drug treatment. Reduced D(1) receptor density in SIR animals was exacerbated by haloperidol, but unaltered by clozapine, without changes in pK(D). SIR thus induces opposing effects on frontal cortical NMDA and D(1) radio-receptor binding characteristics, which has direct bearing on the mutual interplay of these receptors in schizophrenia. The ability of SIR to affect NMDA receptor affinity warrants deeper study. Furthermore, at the doses examined, in contrast to haloperidol, clozapine bolsters frontal cortical glutamatergic but stabilizes D(1) dopaminergic pathways in a neurodevelopmental animal model of schizophrenia, possibly explaining the atypical clinical characteristics of this drug.

Topics: Aging; Analysis of Variance; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dopamine Antagonists; Frontal Lobe; Haloperidol; Male; Random Allocation; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1; Receptors, N-Methyl-D-Aspartate; Schizophrenia; Social Isolation

Using cocaine-sensitized mice as a model for psychosis, this study investigated whether subchronic treatment with clozapine could affect the sensitized state of the animals and examined the accompanying molecular changes in the brain. To induce sensitization, ICR mice (n=44) were treated with cocaine for 5 days. After 7 days of withdrawal, sensitization was confirmed by a cocaine challenge. Then, the sensitized animals were treated with clozapine for 5 days and rechallenged with cocaine. The frontal cortices were removed from the mice (n=16) 24 h after the last challenge, and the phosphorylation status of some key signaling molecules was investigated. Compared with the sensitized mice receiving the vehicle treatment, the sensitized mice receiving subchronic clozapine showed less locomotor activity, with an activity level similar to that of non-sensitized mice. However, clozapine did not directly affect the stimulatory effect of cocaine. Clozapine also reversed some of the sensitization-induced biochemical changes, including increased phosphorylation of GSK-3beta and CREB, in the frontal cortex. Subchronic treatment with clozapine apparently de-sensitized the sensitized mice. The long-term effect of clozapine on stimulant-induced sensitization may be related to the therapeutic effect of the drug as an antipsychotic agent.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Cocaine; CREB-Binding Protein; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Extracellular Signal-Regulated MAP Kinases; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Male; Mice; Mice, Inbred ICR; Motor Activity; Oncogene Protein v-akt; Prefrontal Cortex; Signal Transduction; Substance Withdrawal Syndrome

Schizophrenia is characterized by disturbances in attention and information processing that can be measured by latent inhibition (LI). Research has implicated significant aberrations in dopaminergic (DA) neurotransmission in this disorder.. The objectives of this study were as follows: to probe whether bupropion disrupts LI; to compare its efficacy to the effects of GBR12783 (specific DA uptake inhibitor) and to amphetamine (DA releaser); to test if antipsychotics would reverse LI deficits induced by bupropion, GBR12783, and amphetamine; and to probe if rolipram (phosphodiesterase-4 inhibitor), which increases cyclic AMP (cAMP) similarly to antipsychotics, effectively corrects drug-induced LI deficits. Based on its efficacy in drug addiction, we also asked if bupropion could block the effect of amphetamine.. LI was measured in a conditioned emotional response procedure by comparing suppression of drinking in response to a noise in C57BL/6J mice. Mice previously received 0 (nonpreexposed) or 40 noise exposures (preexposed) followed by two or four noise-foot shock pairings.. Bupropion abolished LI in mice, which was corrected by rolipram, but not by haloperidol and clozapine. GBR12783 and amphetamine, but not antidepressants, also disrupted LI, and this was reversed by antipsychotics and rolipram. Both bupropion and amphetamine disrupted LI via conditioning session. Paradoxically, bupropion and GBR12783 also blocked the amphetamine-induced LI deficit.. Efficacy of rolipram but not antipsychotics to reverse the effects of bupropion suggests novel cAMP-dependent and D(2) receptor-independent mechanisms of the bupropion-induced LI deficit. Further detailed biochemical analysis of bupropion-induced LI deficit might be a fruitful approach in developing new antipsychotics.

Topics: Amphetamine; Animals; Bupropion; Clozapine; Conditioning, Psychological; Disease Models, Animal; Dopamine Agonists; Dopamine Uptake Inhibitors; Drug Interactions; Haloperidol; Inhibition, Psychological; Male; Mice; Mice, Inbred C57BL; Neural Inhibition; Phosphodiesterase 4 Inhibitors; Piperazines; Rolipram; Schizophrenic Psychology

Converging evidence indicates that prenatal exposure to immune challenge can induce long-term cognitive deficits relevant to schizophrenia. Such cognitive impairments may be related to deficient hippocampal neurogenesis at adult age.. In the present study, we sought evidence for the possibility that chronic treatment with the reference atypical antipsychotic drug clozapine may improve prenatal infection-induced cognitive dysfunctions by stimulating adult hippocampal neurogenesis.. This hypothesis was tested in a well-established mouse model of prenatal immune challenge which is based on prenatal administration of the viral mimic, polyriboinosinic-polyribocytidilic acid (PolyI:C).. We found that maternal PolyI:C (5 mg/kg, i.v.) exposure on gestation day 17 led to significant spatial working memory impairment and reduced hippocampal neurogenesis in the resulting offspring at adult age. The latter effect was apparent in postmortem immunohistochemical analyses of the cell proliferation marker bromodeoxyuridine and the microtubule-associated protein doublecortin, a marker of newborn neuronal cells. Chronic (3 weeks) administration of clozapine (5 mg/kg/day, i.p.) significantly improved the prenatal PolyI:C-induced working memory deficits, while at the same time, it negatively affected working memory performance in adult offspring born to control mothers. These bidirectional cognitive effects of clozapine were not paralleled by concomitant effects on adult hippocampal neurogenesis.. Our findings do not support the hypothesis that the atypical antipsychotic drug clozapine may influence cognitive functions by acting on adult neurogenesis in the hippocampus, regardless of whether the drug is administered to subjects with or without a neurodevelopmental predisposition to adult neuropathology.

Topics: Animals; Antipsychotic Agents; Cell Count; Clozapine; Disease Models, Animal; Female; Hippocampus; Male; Memory Disorders; Memory, Short-Term; Mice; Mice, Inbred C57BL; Neurogenesis; Polynucleotides; Pregnancy; Pregnancy Complications, Infectious; Prenatal Exposure Delayed Effects

Elevated brain levels of apolipoprotein D (ApoD) correlate with improved neurological recovery after experimental stroke. Hence, a pharmacological induction of ApoD in the postischemic brain could be beneficial for recovery after stroke. Here we investigated the effect of Clozapine, a compound that increases the expression of ApoD, in two rat models of experimental stroke. Rats were subjected to permanent occlusion of the middle cerebral artery (pMCAO) and treated with Clozapine (i.p. 10 mg/kg body weight) or saline for 8 or 28 days starting on the second day after MCAO. ApoD levels increased by 35% in the peri-infarct area after 10 and 30 days after pMCAO, mainly in neuron-specific nuclear protein (NeuN) positive neurons and glial fibrillary acidic protein (GFAP) positive astrocytes. Clozapine did not affect the neurological deficit assessed by the rotating pole test and a grip strength test at 7 days, 14 days, 21 days, and 28 days after pMCAO. Functional outcome and the infarct size were similar in rats subjected to transient MCAO and injected with Clozapine (i.p. 10 mg/kg body weight) or saline for 26 days starting on the second day after tMCAO. We conclude that Clozapine affects cellular processes involved in peri-infarct tissue reorganization, but does not affect functional recovery after MCAO.

Topics: Animals; Apolipoproteins D; Blotting, Western; Clozapine; Disease Models, Animal; Fluorescent Antibody Technique; Infarction, Middle Cerebral Artery; Male; Microscopy, Confocal; Neuroprotective Agents; Rats; Rats, Wistar; Recovery of Function; Stroke

Individuals receiving clozapine treatment for schizophrenia complain of drooling. Reports on salivary flow measurements are contradictory in humans and lacking in animals. Clozapine has affinity for several different receptor types and may, hypothetically, both stimulate and inhibit salivary secretion. In rats, intravenous clozapine evoked a long-lasting secretion, being more prominent from submandibular than from parotid glands. Chronic denervation enhanced the responses. Clozapine acted on muscarinic (M1-) receptors of acinar cells, independent of central nervous mechanisms, pre-synaptic intraglandular events, or circulating catecholamines. A fraction of the methacholine- and parasympathetic-nerve-evoked secretion was abolished by clozapine at doses below those evoking secretion. Sympathetic-nerve-evoked secretion was partially reduced by clozapine, due to antagonistic action on alpha-adrenoceptors; the beta-adrenoceptor-mediated response persisted. Subsecretory doses of clozapine enhanced secretion induced by the beta-adrenoceptor agonist isoprenaline. The overall actions of clozapine suggest that, in clozapine-treated humans, salivation is increased during sleep and at rest, but is decreased during meals.

Topics: Animals; Antipsychotic Agents; Autonomic Denervation; Cholinergic Agents; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Parotid Gland; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, beta; Receptors, Muscarinic; Saliva; Salivation; Sialorrhea; Submandibular Gland

Growing evidence indicates the role of the thalamus in schizophrenia. The ventral part of the thalamus has been investigated in a few post-mortem studies, suggesting a possible neurodevelopmental etiology of the reduced neuron number.. Here we adapt a neurodevelopmental animal model, the neonatal excitotoxic brain lesion, to the ventral thalamus (VT) of Sprague-Dawley rats. At postnatal day (PD) 7 male pups were bilaterally infused into the VT using ibotenic acid (IBA) or artificial cerebrospinal fluid. Repeated measurements of prepulse inhibition (PPI) of the acoustic startle response, reviewed as a measure of sensorimotor gating deficits in neuropsychiatric disorders such as schizophrenia, were performed during puberty and adulthood.. IBA animals showed lower PPI (p<0.001) compared to controls. The extent of VT lesions correlated negatively with PPI levels (p<0.001). PPI deficits in IBA animals were observed at PD 43 and PPI levels increased significantly after puberty without reaching control levels. Acute or subchronic clozapine treatment did not significantly restore low PPI in IBA rats.. The present data suggest that the VT may be involved in the PPI deficits observed in schizophrenia.

Topics: Age Factors; Aging; Animals; Animals, Newborn; Antipsychotic Agents; Clozapine; Disease Models, Animal; Excitatory Amino Acid Agonists; Ibotenic Acid; Male; Rats; Reflex, Startle; Schizophrenia; Sensory Gating; Thalamus

Women with schizophrenia have later onset and better response to antipsychotic drugs (APDs) than men during reproductive years, but the menopausal period is associated with increased symptom severity and reduced treatment response. Estrogen replacement therapy has been suggested as beneficial but clinical data are inconsistent. Latent inhibition (LI), the capacity to ignore irrelevant stimuli, is a measure of selective attention that is disrupted in acute schizophrenia patients and in rats and humans treated with the psychosis-inducing drug amphetamine and can be reversed by typical and atypical APDs. Here we used amphetamine (1 mg/kg)-induced disrupted LI in ovariectomized rats to model low levels of estrogen along with hyperfunction of the dopaminergic system that may be occurring in menopausal psychosis, and tested the efficacy of APDs and estrogen in reversing disrupted LI. 17beta-Estradiol (50, 150 microg/kg), clozapine (atypical APD; 5, 10 mg/kg), and haloperidol (typical APD; 0.1, 0.3 mg/kg) effectively reversed amphetamine-induced LI disruption in sham rats, but were much less effective in ovariectomized rats; 17beta-estradiol and clozapine were effective only at high doses (150 microg/kg and 10 mg/kg, respectively), whereas haloperidol failed at both doses. Haloperidol and clozapine regained efficacy if coadministered with 17beta-estradiol (50 microg/kg, an ineffective dose). Reduced sensitivity to dopamine (DA) blockade coupled with spared/potentiated sensitivity to DA stimulation after ovariectomy may provide a novel model recapitulating the combination of increased vulnerability to psychosis with reduced response to APD treatment in female patients during menopause. In addition, our data show that 17beta-estradiol exerts antipsychotic activity.

Topics: Amphetamine; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dopamine; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Drug Interactions; Estradiol; Estrogens; Female; Haloperidol; Inhibition, Psychological; Ovariectomy; Psychotic Disorders; Rats; Rats, Wistar; Statistics, Nonparametric; Water Deprivation

The biological underpinnings of schizophrenic polydipsia are poorly understood.. This study is aimed at fulfilling the requisites of an experimental model of this syndrome through the quinpirole (QNP) induction of non-regulatory drinking in rats.. In a first experiment, clozapine (10 and 40 mg/kg p.o.) was substituted for haloperidol during the last 5 days of 10 days QNP (0.5 mg/kg i.p.) administration and water intake measured at 5 h. In a second experiment, animals treated with QNP alone or in combination with clozapine were assessed for water intake and prepulse inhibition (PPI). Expression of genes coding for the dopaminergic D2 receptor, as well as for the early genes BDNF (brain-derived neurotrophic factor) and c-Fos in prefrontal cortex, hippocampus, and striatum was also evaluated.. Clozapine prevented QNP-induced drinking at 10 and 40 mg/kg, but only at 40 mg/kg when it was substituted for haloperidol. In the second experiment, QNP-treated rats showed both non-regulatory drinking and PPI disruption. Both these effects were prevented by clozapine 40 mg/kg. QNP-reduced BDNF expression in the hippocampus and increased c-Fos in the prefrontal cortex. This effect was prevented by clozapine. Given by itself, clozapine reduced the expression of both D2 receptors and BDNF in the prefrontal cortex and striatum.. The present study lends further support to the hypothesis that non-regulatory drinking induced by QNP in rats is a robust and reliable pharmacological effect that might model psychotic polydipsia also in its sensitivity to clozapine.

Topics: Animals; Antipsychotic Agents; Brain; Brain-Derived Neurotrophic Factor; Clozapine; Disease Models, Animal; Dopamine Agonists; Dose-Response Relationship, Drug; Drinking; Gene Expression Regulation; Haloperidol; Male; Proto-Oncogene Proteins c-fos; Quinpirole; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D2; Schizophrenia

Obstetric complications play a role in the pathophysiology of schizophrenia. However, the biological consequences during neurodevelopment until adulthood are unknown. Microarrays have been used for expression profiling in four brain regions of a rat model of neonatal hypoxia as a common factor of obstetric complications. Animals were repeatedly exposed to chronic hypoxia from postnatal (PD) day 4 through day 8 and killed at the age of 150 days. Additional groups of rats were treated with clozapine from PD 120-150. Self-spotted chips containing 340 cDNAs related to the glutamate system ("glutamate chips") were used. The data show differential (up and down) regulations of numerous genes in frontal (FR), temporal (TE) and parietal cortex (PAR), and in caudate putamen (CPU), but evidently many more genes are upregulated in frontal and temporal cortex, whereas in parietal cortex the majority of genes are downregulated. Because of their primary presynaptic occurrence, five differentially expressed genes (CPX1, NPY, NRXN1, SNAP-25, and STX1A) have been selected for comparisons with clozapine-treated animals by qRT-PCR. Complexin 1 is upregulated in FR and TE cortex but unchanged in PAR by hypoxic treatment. Clozapine downregulates it in FR but upregulates it in PAR cortex. Similarly, syntaxin 1A was upregulated in FR, but downregulated in TE and unchanged in PAR cortex, whereas clozapine downregulated it in FR but upregulated it in PAR cortex. Hence, hypoxia alters gene expression regionally specific, which is in agreement with reports on differentially expressed presynaptic genes in schizophrenia. Chronic clozapine treatment may contribute to normalize synaptic connectivity.

Topics: Animals; Animals, Newborn; Antipsychotic Agents; Brain; Carboxypeptidases; Clozapine; Disease Models, Animal; Gene Expression Profiling; Gene Expression Regulation; Hypoxia; Neural Inhibition; Neuropeptide Y; Oligonucleotide Array Sequence Analysis; Rats; Rats, Sprague-Dawley; Receptors, Cell Surface; Synaptosomal-Associated Protein 25; Syntaxin 1

Schizophrenia symptoms segregate into positive, negative and cognitive, which exhibit differential sensitivity to drugs. Recent efforts to identify treatments targeting cognitive impairments in schizophrenia have directed attention to the cholinergic system for its well documented role in cognition. Relatedly, muscarinic antagonists (e.g. scopolamine) produce an 'antimuscarinic syndrome', characterized by psychosis and cognitive impairments. Latent inhibition (LI) is the poorer conditioning to a stimulus resulting from its non-reinforced pre-exposure. LI indexes the ability to ignore irrelevant stimuli and aberrations of this capacity produced by pro-psychotic agents (e.g. amphetamine, MK-801) are used extensively to model attentional impairments in schizophrenia. We recently showed that LI was disrupted by scopolamine at low doses, and this was reversed by typical and atypical antipsychotic drugs (APDs) and the acetylcholinesterase inhibitor physostigmine. Here, at a higher dose (1.5 mg/kg), scopolamine produced an opposite pole of attentional impairment, namely, attentional perseveration, whereby scopolamine-treated rats persisted in expressing LI under strong conditioning that prevented LI expression in controls. Scopolamine-induced persistent LI was reversed by cholinergic and glycinergic cognitive enhancers (physostigmine and glycine) but was resistant to both typical and atypical APDs (haloperidol and clozapine). The latter sets scopolamine-induced persistent LI apart from scopolamine- and amphetamine-induced disrupted LI, which are reversed by both typical and atypical APDs, as well as from other cases of abnormally persistent LI including MK-801-induced persistent LI, which is reversed by atypical APDs. Thus, scopolamine-induced persistent LI may provide a pharmacological LI model for screening cognitive enhancers that are efficient for the treatment of APD-resistant cognitive impairments in schizophrenia.

Topics: Animals; Antipsychotic Agents; Attention; Cholinergic Antagonists; Clozapine; Cognition Disorders; Conditioning, Psychological; Disease Models, Animal; Dose-Response Relationship, Drug; Drinking Behavior; Glycine; Haloperidol; Inhibition, Psychological; Male; Physostigmine; Rats; Rats, Wistar; Schizophrenia; Scopolamine

Clinical observations indicate that antipsychotic action starts early and increases in magnitude with repeated treatment. Animal models that faithfully capture this time course of action are few. Inhibition of hyperlocomotion induced by amphetamine or phencyclidine has been widely used as a screening tool for the antipsychotic activity of a drug. We thus investigated whether repeated antipsychotic treatment could produce an early-onset and progressively increased antagonistic effect on amphetamine or phencyclidine-induced hyperlocomotion as a way of assessing the validity of such models in capturing time course of antipsychotic action. On each of the five consecutive test days, different groups of rats (n=6-7/group) received an initial injection of either haloperidol (0.01-0.10 mg/kg, sc), clozapine (5-20.0 mg/kg, sc), olanzapine (1.0 mg/kg, sc), chlordiazepoxide (10.0 mg/kg, ip) or vehicle (sterile water, sc) 30 min prior to a second injection of either amphetamine (1.5 mg/kg, sc) or phencyclidine (3.2 mg/kg, sc). Motor activity was subsequently monitored for 60 min after amphetamine or phencyclidine treatment. Repeated treatment of haloperidol, clozapine, or olanzapine progressively potentiated inhibition on repeated phencyclidine-induced hyperlocomotion and prolonged this action over the five consecutive days. In contrast, antipsychotic inhibition on repeated amphetamine-induced hyperlocomotion was gradually attenuated and shortened. Repeated treatment of chlordiazepoxide, a benzodiazepine anxiolytic, retained its inhibition on amphetamine-induced hyperlocomotion, but had no effect on phencyclidine-induced one. These results suggest that repeated phencyclidine-induced hyperlocomotion model based on repeated antipsychotic treatment regimen is capable of capturing the progressive increase pattern of antipsychotic treatment seen in the clinic and differentiating antipsychotics from anxiolytics; thus it may serve as a better model for the investigation of the neurobiological mechanisms of action of antipsychotic drugs and delineating the pathophysiology of schizophrenia.

Topics: Amphetamine; Animals; Anti-Anxiety Agents; Antipsychotic Agents; Clozapine; Disease Models, Animal; Haloperidol; Hyperkinesis; Male; Phencyclidine; Rats; Rats, Sprague-Dawley; Time Factors

Abnormal function of NMDA receptors is believed to be a contributing factor to the pathophysiology of schizophrenia. NMDAR subunits and postsynaptic-interacting proteins of these channels are abnormally expressed in some patients with this illness. In mice, reduced NMDAR expression leads to behaviors analogous to symptoms of schizophrenia, but reports of animals with mutations in core postsynaptic density proteins having similar a phenotype have yet to be reported. Here we show that reduced expression of the neuronal RasGAP and NMDAR-associated protein, SynGAP, results in abnormal behaviors strikingly similar to that reported in mice with reduced NMDAR function. SynGAP mutant mice exhibited nonhabituating and persistent hyperactivity that was ameliorated by the antipsychotic clozapine. An NMDAR antagonist, MK-801, induced hyperactivity in normal mice but SynGAP mutants were less responsive, suggesting that NMDAR hypofunction contributes to this behavioral abnormality. SynGAP mutants exhibited enhanced startle reactivity and impaired sensory-motor gating. These mice also displayed a complete lack of social memory and a propensity toward social isolation. Finally, SynGAP mutants had deficits in cued fear conditioning and working memory, indicating abnormal function of circuits that control emotion and choice. Our results demonstrate that SynGAP mutant mice have gross neurological deficits similar to other mouse models of schizophrenia. Because SynGAP interacts with NMDARs, and the signaling activity of this protein is regulated by these channels, our data in dicate that SynGAP lies downstream of NMDARs and is a required intermediate for normal neural circuit function and behavior. Taken together, these data support the idea that schizophrenia may arise from abnormal signaling pathways that are mediated by NMDA receptors.

Topics: Acoustic Stimulation; Analysis of Variance; Animals; Antipsychotic Agents; Behavior, Animal; Behavioral Symptoms; Clozapine; Cross-Over Studies; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Exploratory Behavior; Gene Expression Regulation; Inhibition, Psychological; Locomotion; Memory Disorders; Memory, Short-Term; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Neuropsychological Tests; ras GTPase-Activating Proteins; Reflex, Startle; Schizophrenia; Social Behavior; Stereotyped Behavior

Epidemiological and clinical life cycle studies have indicated that the more favorable illness course and the better response to antipsychotic drugs (APDs) in women with schizophrenia correlate with high levels of estrogen, whereas increased vulnerability to exacerbation and relapse and reduced sensitivity to treatment are associated with low estrogen levels. Accordingly, the estrogen hypothesis of schizophrenia proposes that estrogen has a neuroprotective effect in women vulnerable to schizophrenia.. Latent inhibition (LI), the capacity to ignore stimuli that received nonreinforced preexposure prior to conditioning, is disrupted in acute schizophrenia patients and in rats and humans treated with the psychosis inducing drug amphetamine. Disruption of LI is reversible by typical and atypical APDs. The present study tested whether low levels of estrogen induced by ovariectomy (OVX) would lead to disruption of LI in female rats and whether such disruption would be normalized by estrogen replacement treatment and/or APDs.. Results showed that OVX led to LI disruption, which was reversed by 17beta-estradiol (150 microg/kg) and the atypical APD clozapine (5 mg/kg), but not by the typical APD haloperidol (0.1, 0.2, 0.3 mg/kg). Haloperidol regained efficacy when administered with 17beta-estradiol (50 microg/kg).. These results provide the first demonstration in rats that low levels of hormones can induce a pro-psychotic state that is resistant to at least typical antipsychotic treatment. This constellation may mimic states seen in schizophrenic women during periods associated with low levels of hormones such as the menopause.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Therapy, Combination; Estradiol; Estrogens; Female; Haloperidol; Humans; Ovariectomy; Rats; Rats, Wistar; Schizophrenia

Cognitive deficits in schizophrenia are a major source of dysfunction for which more effective treatments are needed. The vasopressin-deficient Brattleboro (BRAT) rat has been shown to have several natural schizophrenia-like deficits, including impairments in prepulse inhibition and memory. We investigated BRAT rats and their parental strain, Long-Evans (LE) rats, in a social discrimination paradigm, which is an ethologically relevant animal test of cognitive deficits of schizophrenia based upon the natural preference of animals to investigate conspecifics. We also investigated the effects of the atypical antipsychotic, clozapine, and the putative antipsychotic, PD149163, a brain-penetrating neurotensin-1 agonist, on social discrimination in these rats. Adult rats were administered saline or one of the three doses of clozapine (0.1, 1.0, or 10 mg/kg) or PD149163 (0.1, 0.3, or 1.0 mg/kg), subcutaneously. Following drug administration, adult rats were exposed to a juvenile rat for a 4-min learning period. Animals were then housed individually for 30 min and then simultaneously exposed to the juvenile presented previously and a new juvenile for 4 min. Saline-treated LE rats, but not BRAT rats, exhibited intact social discrimination as evidenced by greater time spent exploring the new juvenile. The highest dose of clozapine and the two highest doses of PD149163 restored social discrimination in BRAT rats. These results provide further support for the utility of the BRAT rat as a genetic animal model relevant to schizophrenia and drug discovery. The potential of neurotensin agonists as putative treatments for cognitive deficits of schizophrenia was also supported.

Topics: Animals; Antipsychotic Agents; Brain; Clozapine; Cognition Disorders; Disease Models, Animal; Dose-Response Relationship, Drug; Exploratory Behavior; Male; Mental Disorders; Neurotensin; Rats; Rats, Brattleboro; Rats, Long-Evans; Receptors, Neurotensin; Schizophrenia; Schizophrenic Psychology; Social Behavior

Due to its intrinsic deficiency in prepulse inhibition (PPI), the inbred DBA/2 mouse strain has been considered as an animal model for evaluating antipsychotic drugs. However, the PPI impairment observed in DBA/2 mice relative to the common C57BL/6 strain is confounded by a concomitant reduction in baseline startle reactivity. In this study, we examined the robustness of the PPI deficit when this confound is fully taken into account.. Male DBA/2 and C57BL/6 mice were compared in a PPI experiment using multiple pulse stimulus intensities, allowing the possible matching of startle reactivity prior to examination of PPI. The known PPI-enhancing effect of the antipsychotic, clozapine, was then evaluated in half of the animals, whilst the other half was subjected to two additional schizophrenia-relevant behavioural tests: latent inhibition (LI) and locomotor reaction to the psychostimulants-amphetamine and phencyclidine.. PPI deficiency in DBA/2 relative to C57BL/6 mice was essentially independent of the strain difference in baseline startle reactivity. Yet, there was no evidence that DBA/2 mice were superior in detecting the PPI-facilitating effect of clozapine when startle difference was balanced. Compared with C57BL/6 mice, DBA/2 mice also showed impaired LI and a different temporal profile in their responses to amphetamine and phencyclidine.. Relative to the C57BL/6 strain, DBA/2 mice displayed multiple behavioural traits relevant to schizophrenia psycho- and physiopathology, indicative of both dopaminergic and glutamatergic/N-methyl-D: -aspartic acid receptor dysfunctions. Further examination of their underlying neurobiological differences is therefore warranted in order to enhance the power of this specific inter-strain comparison as a model of schizophrenia.

Topics: Amphetamine; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Motor Activity; Phencyclidine; Phenotype; Reflex, Startle; Schizophrenia; Species Specificity

Second generation antipsychotic drug (SGA) treatment is associated with detrimental effects on glucose metabolism which is often attributed to the development of obesity and insulin resistance. However, we have recently demonstrated that clozapine and quetiapine also have direct effects of glucose metabolism in animals. This study compares clozapine and quetiapine and investigates the effects of these on the development of obesity and the direct effects of these drugs on glucose metabolism compared with those caused by the obesity per se.. Three groups of male Sprague-Dawley rats were fed a high fat/high sugar diet to induce obesity while another three groups were fed a chow diet. One group on each diet was injected daily with vehicle, clozapine or quetiapine and effects on glucose metabolism were monitored.. Clozapine and quetiapine treatment did not directly cause obesity or potentiate diet induced obesity but did induce a preference for the high fat/high sugar diet. Neither drug caused a impairment in insulin tolerance over that caused by obesity but both drugs acutely induced impairments in glucose tolerance that were additive with the effects induced by the diet induced obesity. Both drugs caused increases in glucagon levels and a suppression of GLP-1. We investigated two strategies for restoring GLP-1 signalling. The DPP-IV inhibitor sitagliptin only partially restored GLP-1 levels and did not overcome the deleterious effects on glucose tolerance whereas the GLP-1 receptor agonist exendin-4 normalised both glucagon levels and glucose metabolism.. Our findings indicate that the clozapine and quetiapine induced impairments in glucose tolerance in rats are independent of insulin resistance caused by obesity and that these defects are linked with a suppression of GLP-1 levels. These studies suggest the need to perform follow up studies in humans to determine whether clozapine and quetiapine induce acute derangements in glucose metabolism and whether GLP-1 replacement therapy might be the most appropriate therapeutic strategy for treating derangements in glucose metabolism in subjects taking these drugs.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Body Composition; Body Weight; Clozapine; Dibenzothiazepines; Dietary Fats; Disease Models, Animal; Eating; Exenatide; Food Preferences; Gene Expression Regulation; Glucagon; Glucagon-Like Peptide 1; Glucose; Glucose Tolerance Test; Hypoglycemic Agents; Insulin Resistance; Male; Obesity; Peptides; Pyrazines; Quetiapine Fumarate; Rats; Rats, Sprague-Dawley; Sitagliptin Phosphate; Triazoles; Venoms

Abnormal mesolimbic control of cortical cholinergic activity has been hypothesized to contribute to the cognitive symptoms of schizophrenia. Stimulation of NMDA receptors in nucleus accumbens (NAC) increases acetylcholine (ACh) release in prefrontal cortex (PFC), an activation thought to contribute to attentional processing. Thus, the effects of intra-NAC perfusion of NMDA (250-400 microM) on ACh release in PFC were determined in rats receiving lesions of the ventral hippocampus (VH) as neonates (nVHLX), a neurodevelopmental model of schizophrenia, or as adults (aVHLX). NMDA elevated ACh release (100-150% above baseline) in adults sham-lesioned as neonates or in aVHLX rats. Adult nVHLX were unresponsive to NAC NMDA receptor stimulation. The inability of nVHLX to respond to NMDA emerged over development as a separate experiment demonstrated that evoked ACh release was normal before puberty (100-150% increase) yet, in these same nVHLX animals, absent after puberty. Amphetamine-evoked ACh release was assessed in nVHLX animals to exclude potential limitations in release capacity. Amphetamine produced greater increases in ACh release than in shams, indicating that nVHLX does not impair the capacity of cholinergic neurons to release ACh. Finally, the ability of 13 days of pretreatment with clozapine (1.25 mg/kg/day) to reinstate NMDA-evoked cortical ACh efflux was determined. Clozapine treatment normalized NMDA-evoked ACh release in nVHLX animals. These experiments show that mesolimbic regulation of cortical ACh release is disrupted in postpubertal nVHLX rats and normalized by low-dose treatment of clozapine; supporting the usefulness of nVHLX animals for research on the neuronal mechanisms underlying the cognitive symptoms of schizophrenia.

Topics: Acetylcholine; Aging; Amphetamine; Animals; Animals, Newborn; Clozapine; Disease Models, Animal; Hippocampus; Ibotenic Acid; Male; Microinjections; N-Methylaspartate; Neural Pathways; Nucleus Accumbens; Prefrontal Cortex; Rats; Rats, Wistar; Schizophrenia; Time Factors

Schizophrenia is a neuropsychiatric disorder of a neurodevelopmental origin manifested symptomatically after puberty. Structural neuroimaging studies show that neuroanatomical aberrations occur before onset of symptoms, raising a question of whether schizophrenia can be prevented. Treatment with atypical antipsychotic drugs before the development of the full clinical phenotype might reduce the risk of transition to psychosis, but it remains unknown whether neuroanatomical abnormalities can be prevented. We used a neurodevelopmental animal model of schizophrenia to assess the efficacy of the atypical antipsychotic clozapine to prevent neuroanatomical deterioration.. Pregnant rats received injection on gestational day 15 with the viral mimic polyriboinosinic-polyribocytidylic acid (PolyI:C) or saline. Structural brain changes in the male offspring were assessed at adolescence and adulthood (35 days and 120 days) with structural neuroimaging. In the second part, male offspring of PolyI:C- and saline-treated dams received daily clozapine (7.5 mg/kg) or saline injection in adolescence (days 34-47) and underwent behavioral testing and imaging at adulthood (from 90 days onward).. In utero exposure to maternal infection led in the offspring to postpubertal emergence of hallmark structural abnormalities associated with schizophrenia, enlarged ventricles, and smaller hippocampus. These abnormalities were not observed in the offspring of mothers who received PolyI:C that were treated with clozapine in adolescence. This was paralleled by prevention of behavioral abnormalities phenotypic of schizophrenia, attentional deficit, and hypersensitivity to amphetamine.. This is the first demonstration that pharmacological intervention during adolescence can prevent the emergence of brain structural changes resulting from in-utero insult.

Topics: Abnormalities, Drug-Induced; Age Factors; Amphetamine; Animals; Antipsychotic Agents; Attention; Brain Diseases; Cerebral Ventricles; Clozapine; Disease Models, Animal; Hippocampus; Inhibition, Psychological; Male; Motor Activity; Poly I-C; Rats; Rats, Wistar; Schizophrenia

To explore the correlation between signs similar to schizophrenia in mice after ketamine administration and the expressions of NRG1 and ErbB4 mRNA in order to explain the possible pathogenesis of schizophrenia.. Fifty KM mice were randomly divided into 5 groups which were administered intraperitoneally with saline, clozapine and different dosages ketamine. The ketamine groups were administered intraperitoneally with low dosage (25 mg/kg), middle dosage (50 mg/kg) and high dosage (100 mg/kg) one time every day for 7 days. After administration of 100 mg/kg ketamine for 7 days, the clozapine group was introgastrically administered 20 mg/kg with clozapine one time every day for 7 days. The pathological changes of hippocampus neurons were observed by HE stain. The expressions of the NRG1 and ErbB4 mRNA in hippocampus were detected by reverse transcriptase polymerase chain reaction (RT-PCR).. In the group with high dosage of ketamine, the levels of NRG1 and ErbB4 mRNA were significantly lower than that of the group with saline.. Ketamine may induce signs similar to schizophrenia in KM mice. The mechanism may be involved in the reduction of NRG1 and ErbB4 mRNA expression.

Topics: Animals; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; ErbB Receptors; Hippocampus; Ketamine; Male; Mice; Neuregulin-1; Neurons; Random Allocation; Receptor, ErbB-4; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Schizophrenia

cis-4-(Piperazin-1-yl)-5,6,7a,8,9,10,11,11a-octahydrobenzofuro[2,3-h]quinazolin-2-amine, 4 (A-987306) is a new histamine H(4) antagonist. The compound is potent in H(4) receptor binding assays (rat H(4), K(i) = 3.4 nM, human H(4) K(i) = 5.8 nM) and demonstrated potent functional antagonism in vitro at human, rat, and mouse H(4) receptors in cell-based FLIPR assays. Compound 4 also demonstrated H(4) antagonism in vivo in mice, blocking H(4)-agonist induced scratch responses, and showed anti-inflammatory activity in mice in a peritonitis model. Most interesting was the high potency and efficacy of this compound in blocking pain responses, where it showed an ED(50) of 42 mumol/kg (ip) in a rat post-carrageenan thermal hyperalgesia model of inflammatory pain.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzofurans; Carrageenan; Disease Models, Animal; Drug Design; Drug Evaluation, Preclinical; Humans; Hyperalgesia; Ligands; Mice; Molecular Structure; Pain; Peritonitis; Quinazolines; Rats; Receptors, G-Protein-Coupled; Receptors, Histamine; Receptors, Histamine H4; Stereoisomerism; Structure-Activity Relationship

Polydipsia is a severe complication of long-term schizophrenia and, despite its unknown pathogenesis, is empirically treated with typical or atypical antipsychotics. In the rat, nonregulatory water intake is induced by repeated administration of amphetamine-like compounds or by the D2/3 agonist, quinpirole.. This study is aimed at determining the potential activity of antipsychotic compounds with different affinities for D2 receptors in preventing and/or reversing quinpirole-induced polydipsia.. Male Sprague-Dawley rats were treated with five injections of quinpirole (0.5 mg/kg i.p.) to induce polydipsia. The oral effects of haloperidol, olanzapine, clozapine, and ST2472 on QNP-induced polydipsia were analyzed in the following two schedules. In the preventive schedule, haloperidol (0.2, 0.4, and 0.8 mg/kg), olanzapine (1.5, 3, and 6 mg/kg), ST2472 (1 and 2 mg/kg), and clomipramine (5, 10, and 20 mg/kg) were given in combination with quinpirole from day 1 to day 5. In the reversal schedule, rats showing quinpirole-induced polydipsia on the third day received haloperidol (0.4 mg/kg), olanzapine (1.5 and 3 mg/kg), clozapine (10, 20, and 40 mg/kg), ST2472 (1, 2, 5, and 10 mg/kg), and clomipramine (5, 10, and 20 mg/kg) before quinpirole on days 4 and 5.. Haloperidol both prevented and reversed quinpirole-induced polydipsia, whereas olanzapine and ST2472 only reversed it. Clomipramine prevented but did not reverse quinpirole-induced polydipsia, and clozapine did not reverse it either.. We suggest that, once developed, polydipsia is governed by dopaminergic D2 mechanisms. In contrast, either an increase in the serotoninergic tone or an inhibition of D2 receptors can modulate the development of quinpirole-induced excessive drinking.

Topics: Administration, Oral; Animals; Antipsychotic Agents; Benzodiazepines; Clomipramine; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drinking; Haloperidol; Male; Olanzapine; Piperazines; Pyrroles; Quinpirole; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D2; Thiazepines

Schizophrenic patients demonstrate prominent negative and cognitive symptoms that are poorly responsive to antipsychotic treatment. Abnormal glutamatergic neurotransmission may contribute to these pathophysiological dimensions of schizophrenia.. We examined the involvement of the glycine coagonist site on the N-methyl-D: -aspartate receptor (NMDAR) glycine coagonist site in the modulation of negative and cognitive endophenotypes in mice.. Behavioral phenotypes relevant to schizophrenia were assessed in Grin1(D481N) mice that have reduced NMDAR glycine affinity.. Grin1(D481N) mutant mice showed abnormally persistent latent inhibition (LI) that was reversed by two agents that enhance NMDAR glycine site function, D: -serine (600 mg/kg) and ALX-5407 (1 mg/kg), and by the classical atypical antipsychotic clozapine (3 mg/kg). Similarly, blockade of the NMDAR glycine site with the antagonist L-701,324 (5 mg/kg) induced persistent LI in C57BL6/J mice. In a social affiliations task, Grin1(D481N) mutant animals showed reduced social approach behaviors that were normalized by D: -serine (600 mg/kg). During a nonassociative spatial object recognition task, mutant mice demonstrated impaired reactivity to a spatial change that was reversible by D: -serine (300 and 600 mg/kg) and clozapine (0.75 mg/kg). In contrast, responses to social novelty and nonspatial change remained unaffected, indicating that the Grin1(D481N) mutation induces selective deficits in sociability and spatial discrimination, while leaving intact the ability to react to novelty.. Genetic and pharmacologically induced deficiencies in glycine binding appear to model the impairments in behavioral flexibility, sociability, and spatial recognition related to the negative and cognitive symptoms of schizophrenia. Antipsychotics that target the NMDAR glycine site may be beneficial in treating such psychiatric symptoms.

Topics: Animals; Behavior, Animal; Carrier Proteins; Clozapine; Disease Models, Animal; Glycine; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Nerve Tissue Proteins; Phenotype; Quinolones; Receptors, N-Methyl-D-Aspartate; Recognition, Psychology; Sarcosine; Schizophrenia; Schizophrenic Psychology; Serine; Social Behavior; Space Perception

As a consequence of obstetric complications hypoxia has been discussed as a possible factor in the pathophysiology of schizophrenia. The present study investigated the effects of weak chronic neonatal hypoxia in rats on different behavioural animal models of schizophrenia.. (1) After neonatal hypoxia, half of the pups were fostered by normally treated nurse animals to control for possible maternal effects. (2) The animals were tested on postnatal days (PD) 36, 86, 120 and 150 by applying three different behavioural tests: prepulse inhibition (PPI), social interaction and recognition, and motor activity in an open field. (3) Before the PD 150 test, half of the animals had been chronically treated with the antipsychotic drug clozapine (45 mg/kg/day).. Rats exposed to hypoxia as neonates exhibited a deficit in locomotor activity on PD 86, 120, and 150, as well as a PPI deficit on PD 120 and 150 but not before. Chronic treatment with clozapine reverses the hypoxia induced PPI deficit, but not the decreased locomotor activity. In a second experiment, clozapine was chronically administered before PD 120 and blocked the development of the PPI deficit in the animals exposed to hypoxia.. The time course of the hypoxia-induced PPI deficit and reversibility by clozapine supports the validity of our animal model and the hypothesis that hypoxia as an obstetric complication is an important factor in the pathophysiology of schizophrenia.

Topics: Acoustic Stimulation; Age Factors; Animals; Animals, Newborn; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Hypoxia; Inhibition, Psychological; Interpersonal Relations; Motor Activity; Rats; Rats, Sprague-Dawley; Reflex, Startle

Sensorimotor gating disruptions are seen in various psychiatric illnesses with putatively different pathologies, including schizophrenia and bipolar disorder. Interestingly, mice lacking the dopamine (DA) transporter (DAT) gene display markedly increased levels of DA, deficits in sensorimotor gating, and hyperactivity relative to wild-type mice. Atypical antipsychotics are effective treatments of schizophrenia and manic symptoms, presumably in part by antagonizing DA receptors. Here we report that treatment with clozapine (3 mg/kg) or quetiapine (2.5 mg/kg) attenuated prepulse inhibition deficits in male DAT knockout mice. Thus male DAT knockout mice may provide a useful animal model for predicting the efficacy of novel drugs in treating psychiatric illnesses characterized by a dysregulated DA system.

Topics: Animals; Antipsychotic Agents; Clozapine; Dibenzothiazepines; Disease Models, Animal; Dopamine Plasma Membrane Transport Proteins; Injections, Intraperitoneal; Mice; Mice, Knockout; Mice, Mutant Strains; Quetiapine Fumarate; Reflex, Startle; Schizophrenia

Phospholipase C-beta1 (PLC-beta1) is a rate-limiting enzyme implicated in postnatal-cortical development and neuronal plasticity. PLC-beta1 transduces intracellular signals from specific muscarinic, glutamate and serotonin receptors, all of which have been implicated in the pathogenesis of schizophrenia. Here, we present data to show that PLC-beta1 knockout mice display locomotor hyperactivity, sensorimotor gating deficits as well as cognitive impairment. These changes in behavior are regarded as endophenotypes homologous to schizophrenia-like symptoms in rodents. Importantly, the locomotor hyperactivity and sensorimotor gating deficits in PLC-beta1 knockout mice are subject to beneficial modulation by environmental enrichment. Furthermore, clozapine but not haloperidol (atypical and typical antipsychotics, respectively) rescues the sensorimotor gating deficit in these animals, suggesting selective predictive validity. We also demonstrate a relationship between the beneficial effects of environmental enrichment and levels of M1/M4 muscarinic acetylcholine receptor binding in the neocortex and hippocampus. Thus we have demonstrated a novel mouse model, displaying disruption of multiple postsynaptic signals implicated in the pathogenesis of schizophrenia, a relevant behavioral phenotype and associated gene-environment interactions.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Environment; Hippocampus; Mice; Mice, Knockout; Motor Activity; Neocortex; Phenotype; Phospholipase C beta; Receptors, Muscarinic; Schizophrenia; Schizophrenic Psychology

Sub-chronic phencyclidine (PCP) treatment mimics certain aspects of schizophrenia symptomology in rats. However, there is a marked lack of attempts to model negative symptomology such as social behaviour deficits in female rats. This study was conducted to assess whether sub-chronic PCP treatment produces social interaction deficits in female rats and to ascertain if these deficits can be reversed by either typical (haloperidol) or atypical (clozapine and ziprasidone) antipsychotics.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Drug Interactions; Excitatory Amino Acid Antagonists; Female; Haloperidol; Matched-Pair Analysis; Phencyclidine; Piperazines; Rats; Rats, Inbred Strains; Schizophrenia; Schizophrenic Psychology; Social Behavior; Social Behavior Disorders; Thiazoles

The absence of effective cognition enhancers for the treatment of patients with schizophrenia limits the validation of animal models and behavioral tests used for drug finding and characterization. However, low doses of haloperidol and clozapine were documented to produce moderately beneficial effects in patients. Therefore, this experiment was designed to determine the attentional effects of such treatments in a repeated-amphetamine (AMPH) animal model. Animals were trained in an operant-sustained attention task and underwent a 40-day pretreatment period with saline or increasing doses (1-10 mg per kg) of AMPH. After regaining baseline performance following 10 days of saline treatment, animals were treated with haloperidol (0.025 mg per kg), clozapine (2.5 mg per kg), or vehicle for 10 days. Furthermore, the effects of AMPH challenges (1.0 mg per kg) were assessed. In AMPH-pretreated animals, the administration of AMPH challenges resulted in the disruption of attentional performance. Treatment with haloperidol and clozapine attenuated the detrimental performance effects of these challenges, with clozapine exhibiting more robust attenuation. Furthermore, clozapine, but not haloperidol, impaired the performance of control animals. In contrast, the performance of AMPH-pretreated animals remained unaffected by clozapine. As this animal model detects the moderately beneficial cognitive effects of haloperidol and clozapine, it may be useful for preclinical research designed to detect and characterize treatments for the cognitive symptoms of schizophrenia.

Topics: Animals; Attention; Clozapine; Cognition; Cognition Disorders; Disease Models, Animal; Haloperidol; Male; Psychomotor Performance; Rats; Rats, Sprague-Dawley; Schizophrenia; Treatment Outcome

The chakragati (ckr) mouse, which was serendipitously created as a result of a transgenic insertional mutation, has been proposed as a model of aspects of schizophrenia. The mice exhibit circling, hyperactivity, reduced social interactions, and enlarged lateral ventricles, which parallel aspects of the pathophysiology of schizophrenia. Deficits in sensorimotor gating and processing of the relevance of stimuli are core features of schizophrenia, which underlie many of the symptoms presented. Measures of prepulse inhibition (PPI) and latent inhibition (LI) can assess sensorimotor gating and processing of relevance in both humans and animal models. We investigated PPI of acoustic startle and LI of aversive conditioning in wild-type, heterozygous, and ckr mice. The ckr mice, which are homozygous for the transgene insertion, but not heterozygous littermates, showed impaired PPI in the absence of any difference in acoustic startle amplitude and showed deficits in LI of conditioning of a light stimulus to footshock, measured as suppression of licking for water in water-restricted mice. Together with the previous evidence for hyperactivity, reduced social interactions, and enlarged lateral ventricles, these data lend further support to the suggestion that the ckr mouse has utility as an animal model of aspects of schizophrenia.

Topics: Acoustic Stimulation; Animals; Antipsychotic Agents; Clozapine; Conditioning, Psychological; Disease Models, Animal; Electroshock; Female; Haloperidol; Male; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Transgenic; Neural Inhibition; Reflex, Startle; Risperidone; Schizophrenia

While clozapine is the acknowledged superior pharmacotherapeutic for the treatment of schizophrenia, the side effect profile, which includes potentially fatal complications, limits its usefulness. Central administration of clozapine directly into the brain could circumvent many of the side effect issues due to the dramatic reduction in dose and the limitation of the drug primarily to the CNS. The present study demonstrates that clozapine can be formulated as a stable solution at physiological pH, which does not have in vitro neurotoxic effects at concentrations which may be effective at treating symptoms. Acute central administration improved auditory gating deficits in a mouse model of schizophrenia-like deficits. Assessment of behavioral alterations in rats receiving chronic central infusions of clozapine via osmotic minipump was performed with the open field and elevated plus mazes. Neither paradigm revealed any detrimental effects of the infusion. While these data represent only an initial investigation, they none-the-less suggest that central administration of clozapine may be a viable alternate therapeutic approach for schizophrenia patients which may be effective in symptom reduction without causing behavioral or neurotoxic effects.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; Acoustic Stimulation; Animals; Antipsychotic Agents; Behavior, Animal; beta-Cyclodextrins; Cell Survival; Cells, Cultured; Chemistry, Pharmaceutical; Clozapine; Disease Models, Animal; Drug Design; Evoked Potentials, Auditory; Exploratory Behavior; Hippocampus; Humans; In Vitro Techniques; Injections, Intraventricular; Male; Maze Learning; Mice; Mice, Inbred DBA; Neurotoxicity Syndromes; Rats; Rats, Sprague-Dawley; Reflex, Startle; Schizophrenia; Schizophrenic Psychology

Short-term (<45 days) treatment studies in rats have reported increased oxidative stress and oxidative (i.e., oxygen free radical-mediated) neural cell injury with typical antipsychotics such as haloperidol, but not with the atypicals such as clozapine, olanzapine or risperidone. However, now these and several other atypical antipsychotics that differ in their neurotransmitter receptor affinity profiles are being used for a long-term treatment of schizophrenia. Therefore, understanding of their long-term treatment effects on the expression of antioxidant enzymes and oxidative neural cell injury in rats may be important to explain the possible differential mechanisms underlying their long-term clinical and side effects profiles. The effect of 90 and 180 day exposure to haloperidol (HAL, 2mg/kg/day), a representative typical antipsychotic was compared to exposure to chlorpromazine (CPZ, 10mg/kg/day), ziprasidone (ZIP, 12mg/kg/day), risperidone (RISP, 2.5mg/kg/day), clozapine (CLOZ, 20mg/kg/day) or olanzapine (OLZ, 10mg/kg/day) on the expression of antioxidant defense enzymes and levels of lipid peroxidation in the rat brain. The drug-induced effects on various antioxidant defense enzymes; manganese-superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD) and catalase (CAT) were assessed by determination of their enzymatic activity and protein content. Immunohistochemical analysis was also carried out to assess the cellular levels of MnSOD and CuZnSOD and cellular morphology. The oxidative membrane damage was assessed by determination of levels of the lipid peroxidation product, hydroxyalkanals (HAEs) in the rat brain. Both 90 and 180 days of HAL treatment very significantly decreased the levels of MnSOD (50%) and CuZnSOD (80%) and increased the levels of HAEs compared to vehicle treatment. Smaller reduction was found in CAT (25%) and no change in the glutathione peroxidase (GSHPx). The levels of enzymatic activity correlated generally well with the levels of enzyme protein indicating that the changes were in the expression of net protein. Though atypical antipsychotics like ZIP, RISP and OLZ did not show any change in the HAEs levels up to 90 days, further treatment up to 180 days resulted in significantly increased levels of HAEs in CPZ, ZIP and RISP, but not in OLZ treated rats. Post-treatment with several atypical antipsychotics (OLZ=CLOZ>RISP) for 90 days after 90 day of HAL treatment significantly restored the HAL-induced loss in MnSOD

Topics: Animals; Antipsychotic Agents; Benzodiazepines; Brain; Chlorpromazine; Clozapine; Cross-Over Studies; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Haloperidol; Lipid Peroxidation; Male; Membrane Lipids; Olanzapine; Rats; Rats, Wistar; Risperidone; Schizophrenia; Superoxide Dismutase

Although it is generally accepted that atypical antipsychotics differ in their risk for diabetic side effects, the underlying pharmacological mechanisms are unknown. Studies on the mechanisms of antipsychotic-induced hyperglycemia or insulin resistance are often confounded by the concomitant weight gain and dyslipidemia, known diabetic risk factors. To investigate whether antipsychotics can acutely cause metabolic effects before any change in body composition, we studied the effects of four atypical antipsychotics on whole-body insulin resistance. Using the hyperinsulinemic, euglycemic clamp technique in conscious rats, insulin and somatostatin were infused at a constant rate to provide constant hyperinsulinemia and to suppress pancreatic insulin secretion. Glucose was infused at a variable rate, adjusted to maintain euglycemia. At steady state, animals were administered vehicle (V) or antipsychotic and the glucose infusion rate was monitored as an index of insulin sensitivity. Clamp experiments using radiotracers and studies on glucose uptake into isolated skeletal muscle were conducted to differentiate between effects on hepatic glucose production (HGP) and on peripheral glucose uptake. Olanzapine (OLAN) and clozapine (CLOZ) acutely impaired whole-body insulin sensitivity in a dose-dependent manner (P<0.001 vs V), whereas ziprasidone and risperidone had no effect. CLOZ also induced profound insulin resistance after dosing 10 mg/kg/day for 5 days (P<0.05 vs V). Tracer studies indicated that acute changes mainly reflect increased HGP, consistent with the lack of effect on glucose uptake. OLAN and CLOZ can thus rapidly induce marked insulin resistance, which could contribute to the hyperglycemia and ketoacidosis reported for patients receiving those therapies.

Topics: Acute Disease; Animals; Antipsychotic Agents; Benzodiazepines; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Energy Metabolism; Glucose; Hyperglycemia; Insulin; Insulin Resistance; Liver; Male; Metabolic Syndrome; Muscle, Skeletal; Olanzapine; Rats; Rats, Wistar; Somatostatin

The selective serotonin (5-HT) reuptake inhibitors (SSRIs) represent the first-line pharmacotherapy for obsessive-compulsive disorder (OCD), and atypical antipsychotic drugs, which block 5-HT2A receptors, are used in augmentation strategies. Opiate drugs are also effective in treatment-refractory OCD and Tourette syndrome. The 5-HT2A-related behavior (i.e., head twitch) has been related with tics, stereotypes, and compulsive symptoms observed in Tourette syndrome and OCD.. The aim of this study was to explore whether 5-HT2A-related behavior is affected by atypical opiate drugs.. Head-twitch response was induced in mice by administration of either 5-hydroxytryptophan (5-HTP) or the 5-HT2A/C agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Dose-effect curves of atypical opiate drugs [(+/-)-tramadol, (-)-methadone and levorphanol], morphine, and other psychoactive drugs (fluvoxamine, desipramine, nefazodone, and clozapine) were performed. Opioid mechanisms were investigated by administration of naloxone.. All the opiates tested reduced both 5-HTP and DOI-induced behavior in a naloxone-reversible fashion, atypical opiates being more effective. The effects of the other drugs depended on the protocol, clozapine being the most effective.. Combined 5-HT and opioid properties result in a greater efficacy in antagonizing 5-HT2A-related behavior. These results provide behavioral evidence to support convergent effects of the 5-HT and opioid systems in discrete brain areas, offering the potential for therapeutic advances in the management of refractory stereotypes and compulsive behaviors.

Topics: 5-Hydroxytryptophan; Analgesics, Opioid; Animals; Clozapine; Desipramine; Disease Models, Animal; Dose-Response Relationship, Drug; Fluvoxamine; Indophenol; Levorphanol; Male; Methadone; Mice; Morphine; Naloxone; Narcotic Antagonists; Obsessive-Compulsive Disorder; Piperazines; Receptor, Serotonin, 5-HT2A; Receptor, Serotonin, 5-HT2C; Stereotyped Behavior; Tics; Tourette Syndrome; Tramadol; Triazoles

Atypical antipsychotics improve cognitive function, including working memory, in schizophrenia. Some atypical antipsychotics have been reported to activate the locus coeruleus and induce beta-adrenoceptor antagonist sensitive c-Fos-like immunoreactivity in the prefrontal cortex.. The present study investigated the effects of chronic treatment of rats with risperidone (1 mg kg(-1) day(-1) s.c.), clozapine (10 mg kg(-1) day(-1) s.c.), or acidified saline vehicle control for 2, 4, or 8 weeks on spatial working memory performance in a delayed matching-to-place water maze task with a 60-s inter-trial retention interval with and without acute challenge with propranolol (10 mg/kg i.p.).. Treatment with risperidone for 8 weeks, but not 2 or 4 weeks, significantly improved working memory performance. In contrast, treatment with clozapine for up to 8 weeks did not improve working memory. Acute challenge with propranolol blocked the improvement in working memory produced by chronic treatment with risperidone, but had no significant effect on performance in saline- or clozapine-treated animals.. The delayed matching-to-place water maze task may prove valuable in the investigation of the behavioural pharmacology of the cognitive effects of antipsychotic drugs. These data suggest that beta adrenoceptors may contribute to the cognitive effects of chronic treatment with atypical antipsychotics.

Topics: Adrenergic beta-Antagonists; Analysis of Variance; Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Drug Administration Schedule; Drug Interactions; Male; Maze Learning; Memory; Propranolol; Rats; Rats, Sprague-Dawley; Risperidone; Schizophrenia; Space Perception

MK-801, a glutamergic, N-methyl-D-aspartate (NMDA)-receptor antagonist that mediates neurotransmission and has psychotomimetic properties, giving schizophrenia-like symptom. The objective of this study was to investigate the effects on the thalamic and cortical proteome of one typical (haloperidol) and one atypical (clozapine) antipsychotic drug in interaction with MK-801 in rats. Rats received subcutaneous injections of MK-801 or vehicle (controls) or MK-801 together with concurrent administration of haloperdol or clozapine for eight days. Protein samples from thalamus and cortex were analyzed with two-dimensional gel electrophoresis in combination with mass spectrometry. MK-801 induced alterations in the levels of three proteins in both cortex and thalamus. Clozapine reversed all the protein changes. Haloperidol reversed two. Both antipsychotics induced new protein changes in both cortex and thalamus not seen after MK-801-treatment by alone. In conclusion, the MK-801 animal model shows potential for investigation of different antipsychotic drugs and biochemical treatment effects in schizophrenia.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Drug Combinations; Excitatory Amino Acid Antagonists; Haloperidol; Male; Proteome; Rats; Rats, Sprague-Dawley; Schizophrenia; Serotonin Antagonists; Thalamus

Prior exposure to the psychotomimetic drug phencyclidine (PCP) decreases voluntary sucrose consumption in rats. This may be indicative of reduced reward function, a phenomenon associated with negative schizophrenic symptomatology. Given that atypical antipsychotics have been shown to ameliorate negative symptoms of schizophrenia more effectively than typical neuroleptics, this effect should be reversed by clozapine but not haloperidol. PCP (15 mg/kg) or saline was administered 20 h prior to testing for voluntary sucrose consumption in non-deprived rats. In the acute experiments, rats were treated with clozapine (5 mg/kg), haloperidol (0.2 mg/kg), or vehicle 45 min prior to testing. In the subchronic experiments, rats were treated with clozapine (3 mg/kg, bid), haloperidol (0.5 mg/kg, bid), or vehicle for 10 days prior to PCP administration. Acute clozapine exacerbated the PCP-induced decrease in sucrose consumption without altering water consumption. Acute haloperidol produced an overall decrease in sucrose consumption in both PCP-pretreated and control groups. Subchronic treatment with clozapine, but not haloperidol, reversed PCP-induced decreases in sucrose consumption. The synergistic effect of acute clozapine and PCP may reflect a PCP-induced increase in the reward-reducing properties of CLZ, normally seen only at higher doses. The observation that subchronic clozapine, but not haloperidol, reversed PCP-induced decreases in sucrose consumption supports the hypothesis that this effect of PCP represents a plausible animal model for negative schizophrenic symptomatology.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Eating; Hallucinogens; Haloperidol; Male; Phencyclidine; Rats; Rats, Sprague-Dawley; Reward; Schizophrenia; Sucrose

In humans, the N-methyl-D-aspartate antagonist phencyclidine (PCP) induces behavioral changes that mimic schizophrenia symptoms, including positive and negative symptoms as well as cognitive deficits. In clinic, the cognitive deficits are closely associated with functional outcome. Thus, improvement of cognition may have high impact on patients' daily life.. In the present study, three second-generation antipsychotics (sertindole, risperidone, and clozapine) as well as the classical antipsychotic haloperidol were tested for the ability to reverse PCP-induced cognitive deficits in the Morris' water maze.. The second-generation antipsychotics reversed the PCP-induced cognitive impairment: sertindole (0.63-2.5 mg/kg, s.c.), risperidone (0.04 mg/kg, s.c.; whereas 0.08 and 0.16 mg/kg were without significant effect), and clozapine (0.63 mg/kg, s.c.; while 1.3 mg/kg was without significant effect). The significant effect of sertindole was observed from day 2 onwards, while clozapine and risperidone only had significant effect at day 3. The classical antipsychotic haloperidol (0.010-0.020 mg/kg, s.c.) was ineffective. No compounds influenced swimming speed at the doses used, indicating that motor function was preserved.. These results confirm that repeated PCP administration induces marked cognitive deficits. Further, second-generation antipsychotics like sertindole, clozapine, and risperidone within a certain, often narrow, dose range are able to reverse the impairment and thus might improve cognitive deficits in schizophrenic patients, whereas classical compounds like haloperidol lack this effect. The receptor mechanisms involved in the reversal of PCP's disruptive effect are discussed and likely include a delicate balance between effects on dopamine D(2), 5-HT(2A/6), alpha-adrenergic, muscarinic, and histaminergic H(1) receptors.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Cognition Disorders; Disease Models, Animal; Dose-Response Relationship, Drug; Haloperidol; Imidazoles; Indoles; Male; Maze Learning; Phencyclidine; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Risperidone; Schizophrenic Psychology

Central nervous system dopaminergic mechanisms have been implicated in the cytokine response to stress and sepsis. We here describe the effects of haloperidol or clozapine in the treatment of sepsis induced by cecal ligation and puncture. Male Wistar rats were subjected to the CLP procedure were treated with haloperidol or clozapine and plasma cytokines, myeloperoxidase activity, markers of organ injury and survival was analyzed. The addition of haloperidol or clozapine to basic support did not diminished hepatic, renal, pancreatic or muscular damage observed after sepsis. Neither haloperidol, nor clozapine, modulates pro and antiinflammatory cytokines after sepsis induction. In addition, haloperidol treatment did not diminished myeloperoxidase activity in the kidney, lung or liver, or altered BALF markers of lung damage or inflammatory infiltration. Our data did not support a role of haloperidol or clozapine as an immunomodulator agent in the treatment of sepsis in an animal model of peritonitis.

Topics: Animals; Biomarkers; Clozapine; Disease Models, Animal; Dopamine Antagonists; Haloperidol; Inflammation; Intestinal Perforation; Male; Neutrophil Infiltration; Peritoneum; Rats; Rats, Wistar; Sepsis

Cognitive deficits in schizophrenia are severe and do not respond well to available treatments. The development and validation of animal models of cognitive deficits characterizing schizophrenia are crucial for clarifying the underlying neuropathology and discovery of improved treatments for such deficits.. We investigated whether single and repeated administrations of the psychotomimetic phencyclidine (PCP) disrupt performance in the five-choice serial reaction time task (5-CSRTT), a test of attention and impulsivity. We also examined whether PCP-induced disruptions in this task are attenuated by atypical antipsychotic medications.. A single injection of PCP (1.5-3 mg/kg, s.c., 30-min pre-injection time) had nonspecific response-depressing effects. Repeated PCP administration (2 mg/kg for two consecutive days followed by five consecutive days, s.c., 30-min pre-injection time) resulted in decreased accuracy, increased premature and timeout responding, and increased response latencies. The atypical antipsychotic medications clozapine, risperidone, quetiapine, and olanzapine and the typical antipsychotic medication haloperidol did not disrupt 5-CSRTT performance under baseline conditions except at high doses. The response depression induced by a single PCP administration was exacerbated by acute clozapine or risperidone and was unaffected by chronic clozapine. Importantly, chronic clozapine partially attenuated the performance disruptions induced by repeated PCP administration, significantly reducing both the accuracy impairment and the increase in premature responding.. Disruptions in 5-CSRTT performance induced by repeated PCP administration are prevented by chronic clozapine treatment and may constitute a useful animal model of some cognitive symptoms of schizophrenia.

Topics: Animals; Antipsychotic Agents; Attention; Benzodiazepines; Clozapine; Cognition Disorders; Dibenzothiazepines; Disease Models, Animal; Dose-Response Relationship, Drug; Hallucinogens; Haloperidol; Impulsive Behavior; Male; Olanzapine; Phencyclidine; Quetiapine Fumarate; Rats; Rats, Wistar; Reaction Time; Risperidone; Schizophrenia

The hypo-glutamatergic hypothesis of schizophrenia is based on clinical similarities between schizophrenia and phencyclidine (PCP)-induced psychosis in mentally healthy humans. Sensorimotor gating, as measured by prepulse inhibition (PPI) of the acoustic startle response (ASR), is impaired in schizophrenic patients. In animals, noncompetitive N-methyl-D: -aspartate (NMDA) antagonists such as PCP disrupt PPI in a way that resembles the defect seen in schizophrenia. In a previous study with inbred mouse strains, low PPI levels have been demonstrated in CPB-K mice possessing low levels of hippocampal NMDA receptor densities. The present study was performed to test whether the low magnitude of PPI in CPB-K mice can be reversed by the atypical antipsychotic drug clozapine (CLZ).. Before any treatment, CPB-K mice displayed a significant (p < 0.001) lower level in PPI and a significant (p < 0.001) higher ASR when compared to BALB/cJ mice known to have high hippocampal NMDA receptor densities. Acute and subchronic effects of a 2-week treatment with CLZ at daily doses of 5 and 10 mg/kg intraperitoneally, respectively, did not reveal any significant alteration of PPI levels in CPB-K mice. Nevertheless, the examination of motor behavior during nonstimulus trials provided a positive control for the drug's effectiveness.. In summary, (1) this study confirmed our working hypothesis: Lower levels of hippocampal glutamatergic receptor densities correspond to lower sensorimotor gating in CPB-K mice, and (2) acute or subchronic treatment with CLZ did not elevate low PPI levels in CPB-K mice. Thus, further experiments will concentrate on other antipsychotic drugs to prove the predictive validity of this animal model.

Topics: Acoustic Stimulation; Analysis of Variance; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Hippocampus; Humans; Injections, Intraperitoneal; Male; Mice; Mice, Inbred BALB C; Mice, Inbred Strains; Neural Inhibition; Psychomotor Performance; Receptors, N-Methyl-D-Aspartate; Reflex, Startle; Schizophrenia; Schizophrenic Psychology; Time Factors

We previously reported that vasopressin deficient Brattleboro (BRAT) rats exhibit deficits in prepulse inhibition (PPI) of the startle reflex that are consistent with PPI deficits exhibited by patients with schizophrenia and other neuropsychiatric disorders. Preliminary evidence indicates that this may be the basis of a predictive model for antipsychotic drug efficacy. Here we report the effects of acute and chronic administration of established and putative antipsychotics on these PPI deficits. BRAT rats, compared to their derivative strain, Long Evans rats, exhibited significantly decreased PPI and startle habituation consistent with patients with schizophrenia and other neuropsychiatric disorders. The second generation antipsychotics, risperidone and clozapine as well as a neurotensin agonist (PD149163) increased BRAT rat PPI, whereas saline, the typical antipsychotic, haloperidol, and a vasopressin analog (1-desamino-D-arginine vasopressin) did not. Similar to their effects in humans, chronic administration of antipsychotic drugs produced stronger effects than acute administration. These results further support the BRAT rat as a model of sensorimotor gating deficits with predictive validity for antipsychotics. The model appears to be able to differentiate first generation from second generation antipsychotics, identify putative antipsychotics with novel mechanisms (i.e., peptides) and reasonably model the therapeutic time course of antipsychotic drugs in humans.

Topics: Analysis of Variance; Animals; Antipsychotic Agents; Arginine Vasopressin; Clozapine; Deamino Arginine Vasopressin; Disease Models, Animal; Drug Administration Schedule; Drug Evaluation, Preclinical; Habituation, Psychophysiologic; Haloperidol; Neural Inhibition; Neurotensin; Rats; Rats, Brattleboro; Rats, Long-Evans; Rats, Mutant Strains; Reflex, Startle; Risperidone; Schizophrenia; Statistics, Nonparametric

Gamma-amino-butyric acid (GABA)(B) receptors play a key role in the pathophysiology of psychotic disorders. We previously reported that baclofen, the prototypical GABA(B) agonist, elicits antipsychotic-like effects in the rat paradigm of prepulse inhibition (PPI) of the startle, a highly validated animal model of schizophrenia.. We studied the role of GABA(B) receptors in the spontaneous PPI deficits displayed by DBA/2J mice.. We tested the effects of baclofen (1.25-5 mg/kg, intraperitoneal [i.p.]) in DBA/2J and C57BL/6J mice, in comparison to the antipsychotic drugs haloperidol (1 mg/kg, i.p.) and clozapine (5 mg/kg, i.p.). Furthermore, we investigated the expression of GABA(B) receptors in the brain of DBA/2J and C57BL/6J mice by quantitative autoradiography.. Baclofen dose-dependently restored PPI deficit in DBA/2J mice, in a fashion similar to the antipsychotic clozapine (5 mg/kg, i.p.). This effect was reversed by pretreatment with the GABA(B) antagonist SCH50211 (50 mg/kg, i.p.). In contrast, baclofen did not affect PPI in C57BL/6J mice. Finally, quantitative autoradiographic analyses assessed a lower GABA(B) receptor expression in DBA/2J mice in comparison to C57BL/6J controls in the prefrontal cortex and hippocampus but not in other brain regions.. Our data highlight GABA(B) receptors as an important substrate for sensorimotor gating control in DBA/2J mice and encourage further investigations on the role of GABA(B) receptors in sensorimotor gating, as well as in the pathophysiology of psychotic disturbances.

Topics: Animals; Antipsychotic Agents; Autoradiography; Baclofen; Brain; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; GABA Agonists; Haloperidol; Injections, Intraperitoneal; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Neural Inhibition; Receptors, GABA-B; Reflex, Startle; Schizophrenia

Behavioral despair is a model of high predictivity for antidepressant activity in murids. For some drug targets, guinea pigs exhibit a higher homology to their human counterparts compared to murids.. In this paper, we established a model of behavioral despair namely, the forced swim test (FST) in guinea pigs.. Male guinea pigs underwent the FST similar to rats. Animals received intraperitoneal injections of either vehicle or drugs 24, 4, and 0.5 h before testing. We tested the tricyclic antidepressants desipramine and amitriptyline, the monoamine oxidase inhibitor tranylcypromine, the selective serotonin reuptake inhibitors fluoxetine and paroxetine, and the neurokinin 1 (NK(1)) receptor antagonist, L-733,060, and for comparison the antipsychotic clozapine and the stimulant methamphetamine.. Desipramine (> or =3 mg/kg) and amitriptyline (>10 mg/kg) increased the latency to immobility (LTI) to greater than 230 s, and tranylcypromine (10 mg/kg) it to greater than 190 s. Paroxetine (>0.3 mg/kg) and fluoxetine (>10 mg/kg) also increased LTI significantly but only to greater than 120 s. Methamphetamine (3 mg/kg) completely eliminated immobility, whereas clozapine (5-20 mg/kg) had no effect. L-733,060 (10 mg/kg) increased LTI to 270 s. Doses producing significant effects in FST were investigated in the open field. Antidepressants did not affect locomotion, whereas methamphetamine induced hyperlocomotion.. We demonstrate the suitability of a modified procedure of the FST for a nonmurid species: the guinea pig. Known antidepressants showed similar effects as in rats and mice. It is interesting to note that the NK(1) antagonist L-733,060 increased forced swimming, suggesting its antidepressant potential. Thus, the guinea pig FST allows the study of antidepressant activity also in NK(1) antagonists that cannot be studied appropriately in murids.

Topics: Amitriptyline; Animals; Antidepressive Agents; Antidepressive Agents, Tricyclic; Antipsychotic Agents; Behavior, Animal; Central Nervous System Stimulants; Clozapine; Desipramine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Drugs, Investigational; Fluoxetine; Guinea Pigs; Injections, Intraperitoneal; Male; Methamphetamine; Monoamine Oxidase Inhibitors; Paroxetine; Piperidines; Selective Serotonin Reuptake Inhibitors; Swimming; Tranylcypromine

A new series of dopamine D4 receptor agonists, 1-aryl-3-(4-pyridinepiperazin-1-yl)propanone oximes, was designed through the modification of known dopamine D4 receptor agonist PD 168077. Replacement of the amide group with a methylene-oxime moiety produced compounds with improved stability and efficacy. Structure-activity relationsips (SAR) of the aromatic ring linked to the N-4-piperazine ring confirmed the superiority of 2-pyridine as a core for D4 agonist activity. A two-methylene linker between the oxime group and the N-1-piperazine ring displayed the best profile. New dopamine D4 receptor agonists, exemplified by (E)-1-(4-chlorophenyl)-3-(4-pyridin-2-ylpiperazin-1-yl)propan-1-one O-methyloxime (59a) and (E)-1-(3-chloro-4-fluorophenyl)-3-(4-pyridin-2-ylpiperazin-1-yl)propan-1-one O-methyloxime (64a), exhibited favorable pharmacokinetic profiles and showed oral bioavailability in rat and dog. Subsequent evaluation of 59a in the rat penile erection model revealed in vivo activity, comparable in efficacy to apomorphine. Our results suggest that the oximes provide a novel structural linker for 4-arylpiperazine-based D4 agonists, possessing leadlike quality and with potential to develop a new class of potent and selective dopamine D4 receptor agonists.

Topics: Animals; Benzamides; Binding Sites; Cell Line; Crystallography, X-Ray; Disease Models, Animal; Drug Evaluation, Preclinical; Erectile Dysfunction; Ferrets; Humans; Male; Models, Molecular; Molecular Structure; Oximes; Piperazines; Rats; Rats, Wistar; Receptors, Dopamine D4; Stereoisomerism; Structure-Activity Relationship

Latent inhibition (LI) is the proactive interference of inconsequential preexposure to a stimulus with its ability to signal significant events, and disrupted LI is considered to model positive symptoms of schizophrenia. We have recently shown that lesions of the nucleus accumbens core (NACc), basolateral amygdala (BLA) and orbitofrontal cortex (OFC) produce abnormally persistent LI, and suggested that this phenomenon may model negative symptoms. Here we tested whether NACc, BLA and OFC lesion-induced persistent LI would be reversed by the atypical antipsychotic drug (APD) clozapine but not by the typical APD haloperidol. Because clozapine's action is likely reflecting its 5HT2A receptor antagonism, we also tested whether NACc lesion-induced persistent LI would be reversed by the selective 5HT2A antagonist M100907. LI was measured in a conditioned emotional response procedure by comparing suppression of drinking in response to a tone in rats receiving 0 (non-preexposed) or 40 tone presentations (preexposed) followed by five tone-shock pairings. Under these conditions, control rats did not show LI but all lesioned rats persisted in exhibiting LI, and this was reversed by clozapine but not by haloperidol. In addition, M100907 reversed NACc lesion-induced persistent LI. These two novel phenomena, abnormally persistent LI and its selective reversal by an atypical APD, suggest a novel index of schizophrenia relevant behavioral abnormality and of atypical antipsychotic activity in the LI model. The identification of brain regions whose damage leads to persistent LI in the rat may provide valuable cues on dysfunctional brain circuits involved in negative symptoms and in the action of atypical APDs.

Topics: Amygdala; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Drinking Behavior; Haloperidol; Male; Nerve Net; Neural Inhibition; Nucleus Accumbens; Prefrontal Cortex; Rats; Rats, Wistar; Receptors, Serotonin; Schizophrenia

Maternal viral infection is associated with increased risk for schizophrenia. It is hypothesized that the maternal immune response to viruses may influence fetal brain development and lead to schizophrenia.. To mimic a viral infection, the synthetic double strand RNA polyriboinosinic-polyribocytidilic acid (poly I:C) was administered into pregnant mice. Behavioral evaluations (thigmotaxis, methamphetamine [MAP]-induced hyperactivity, novel-object recognition test [NORT]), sensorimotor gating (prepulse inhibition [PPI]), and biochemical evaluation of the dopaminergic function of the offspring of phosphate-buffered saline (PBS)-treated dams (PBS-mice) and that of poly I:C-treated dams (poly I:C-mice) were examined.. In juveniles, no difference was found between the poly I:C-mice and PBS-mice. However, in adults, the poly I:C-mice exhibited attenuated thigmotaxis, greater response in MAP-induced (2 mg/kg) hyperlocomotion, deficits in PPI, and cognitive impairment in NORT compared with the PBS-mice. Cognitive impairment in the adult poly I:C-mice could be improved by subchronic administration of clozapine (5.0 mg/kg) but not haloperidol (.1 mg/kg). Increased dopamine (DA) turnover and decreased receptor binding of D2-like receptors, but not D1-like receptors, in the striatum were found in adult poly I:C-mice.. Prenatal poly I:C administration causes maturation-dependent increased subcortical DA function and cognitive impairment in the offspring, indicating a neurodevelopmental animal model of schizophrenia.

Topics: Animals; Animals, Newborn; Antibodies, Viral; Brain; Clozapine; Cognition; Cytokines; Disease Models, Animal; Exploratory Behavior; Female; Form Perception; Mental Recall; Methamphetamine; Mice; Mice, Inbred BALB C; Motor Activity; Neural Inhibition; Neuroimmunomodulation; Orientation; Poly I-C; Pregnancy; Pregnancy Complications, Infectious; Pregnancy, Animal; Prenatal Exposure Delayed Effects; Reflex, Startle; Schizophrenia; Virus Diseases

There is growing evidence from both uncontrolled and controlled clinical studies that lamotrigine (LTG) significantly augments clozapine (CLZ) in the treatment of refractory schizophrenia (RS) [Dursun, S.M., McIntosh, D., Milliken, H., 1999. Clozapine plus lamotrigine in treatment-resistant schizophrenia. Arch. Gen. Psychiatry 56, 950; Dursun, S.M., Deakin, J.F.W., 2001. Augmenting antipsychotic treatment with lamotrigine or topiramate in patients with treatment-resistant schizophrenia: a naturalistic case-series outcome study. J. Psychopharmacol. 15, 297-301; Tiihonen, J., Hallikainen, T., Ryynanen, O.P., Repo-Tiihonen, E., Kotilinen, I., Eronen, M., Toivonen, P., Wahlbeck, K., Putkonen, A., 2003. Lamotrigine in treatment-resistant schizophrenia; a randomized placebo-controlled cross over trial. Biol. Psychiatry 54, 1241-1248; Kremer, I., Vass, A., Gorelik, I., Bar, G., Blanaru, M., Javitt, D.C., Heresco-Levy, U., 2004. Placebo-controlled trial of lamotrigine added to conventional and atypical antipsychotics in schizophrenia. Biol. Psychiatry. 56, 441-446]. However, the precise mechanism of action of this synergistic augmentation between clozapine and lamotrigine remains unclear. Therefore, the goal of this research is to explore the mechanism of action of this synergistic interaction between CLZ and LTG, utilizing a pharmacological animal model of schizophrenia by using phencyclidine (PCP). The effects of CLZ plus LTG were assessed by measuring PCP-induced hyper-locomotion and stereotyped behaviours in rats. Adult male rats (250-300 g) were pre-treated via intra-peritoneal (i.p.) injection with vehicle or drug 30 min before a PCP (5 mg/kg) or saline challenge. The behaviours were recorded and analysed for a 90-min period using the Etho Vision-computer based system. PCP produced hyper-locomotion, which was maximal at 30 min. LTG (10 mg/kg) significantly increased hyperlocomotion induced with PCP. However, a combination treatment of CLZ (5 mg/kg) plus LTG (10 mg/kg) significantly blocked the potentiation of PCP-induced hyper-locomotion observed with LTG (10 mg/kg) alone. Furthermore, the PCP-induced locomotion in the combination CLZ plus LTG-treated rats was significantly decreased when compared to vehicle. Therefore, LTG at doses that do not induce ataxia enhanced PCP-induced hyper-locomotion in rats, whereas the combination of LTG and CLZ significantly decreased PCP-induced hyper-locomotion consistent with clinical data.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Drug Interactions; Hyperkinesis; Lamotrigine; Male; Motor Activity; Phencyclidine; Rats; Rats, Sprague-Dawley; Time Factors; Triazines

Clozapine is an effective atypical antipsychotic drug used to treat schizophrenia. It has the advantage of producing fewer extrapyramidal motor side effects than typical antipsychotic drugs such as haloperidol. Schizophrenia involves more than the hallmark symptom of psychosis. Substantial cognitive impairment is also seen. Effective drug treatments against the cognitive impairment of schizophrenia need to be developed. The current study was conducted to determine the effects of clozapine on working memory in the rat neonatal hippocampal lesion model of schizophrenia, which includes symptoms of cognitive impairment. Infant Sprague-Dawley rats were given ibotenic acid lesions of the hippocampus on day 7 of age (using the day of birth as day 0). Controls were given vehicle infusions. In adulthood, the rats were trained on the 8-arm radial maze using the win-shift procedure. After 6 sessions of training, the lesioned rats and their controls were administered repeated injections of saline or clozapine (2.5 mg/kg) for the next 12 sessions of training. The females had significant radial-arm maze choice accuracy impairments caused by either clozapine or the hippocampal lesion, but the combination of the two treatments had no additive effect. The males showed a different pattern of effects. Intact males did not show a significant clozapine-induced impairment, whereas males with hippocampal lesions did show significant clozapine-induced impairment although hippocampal lesions by themselves did not significantly impair male choice accuracy. These data show that clozapine can cause memory impairment and it potentiates rather than reverses hippocampal lesion-induced deficits. There are critical sex-related differences in these effects.

Topics: Analysis of Variance; Animals; Animals, Newborn; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Hippocampus; Ibotenic Acid; Male; Maze Learning; Memory; Pregnancy; Random Allocation; Rats; Rats, Sprague-Dawley; Reaction Time; Schizophrenia; Sex Factors

To characterize a model of atypical antipsychotic drug-induced obesity and evaluate its mechanism.. Chronically, olanzapine or clozapine was self-administered via cookie dough to rodents (Sprague-Dawley or Wistar rats; C57Bl/6J or A/J mice). Chronic studies measured food intake, body weight, adiponectin, active ghrelin, leptin, insulin, tissue wet weights, glucose, clinical chemistry endpoints, and brain dopaminergic D2 receptor density. Acute studies examined food intake, ghrelin, leptin, and glucose tolerance.. Olanzapine (1 to 8 mg/kg), but not clozapine, increased body weight in female rats only. Weight changes were detectable within 2 to 3 days and were associated with hyperphagia starting approximately 24 hours after the first dose. Chronic administration (12 to 29 days) led to adiposity, hyperleptinemia, and mild insulin resistance; no lipid abnormalities or changes in D2 receptor density were observed. Topiramate, which has reversed weight gain from atypical antipsychotics in humans, attenuated weight gain in rats. Acutely, olanzapine, but not clozapine, lowered plasma glucose and leptin. Increases in glucose, insulin, and leptin following a glucose challenge were also blunted.. A model of olanzapine-induced obesity was characterized which shares characteristics of patients with atypical antipsychotic drug-induced obesity; these characteristics include hyperphagia, hyperleptinemia, insulin resistance, and weight gain attenuation by topiramate. This model may be a useful and inexpensive model of uncomplicated obesity amenable to rapid screening of weight loss drugs. Olanzapine-induced weight gain may be secondary to hyperphagia associated with acute lowering of plasma glucose and leptin, as well as the inability to increase plasma glucose and leptin following a glucose challenge.

Topics: Animals; Antipsychotic Agents; Benzodiazepines; Blood Glucose; Body Weight; Clozapine; Disease Models, Animal; Energy Intake; Female; Glucose Tolerance Test; Insulin; Leptin; Male; Mice; Mice, Inbred C57BL; Obesity; Olanzapine; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, Dopamine; Sex Factors

Schizophrenia is associated with abnormalities in glucose metabolism that may lead to insulin resistance and a 3 fold higher incidence of type II diabetes mellitus. The goal of the present studies was to assess the role of insulin-dependent Akt signaling in schizophrenia and in animal and cellular models of insulin resistance. Our studies revealed a functional decrease in insulin receptor (IR)-mediated signal transduction in the dorsolateral prefrontal cortex (BA46) of medicated schizophrenics relative to control patients using post-mortem brain material. We found approximately 50% decreases in the content and autophosphorylation levels of IRbeta and approximately 76-78% decreases in Akt content and activity (pSer(473)-Akt). The inhibition of IRbeta signaling was accompanied by an elevated content of glycogen synthase kinase (GSK)-3 alpha and GSK-3beta without significant changes in phospho-Ser(21/9) GSK-3 alpha/beta levels. A cellular model of insulin resistance was induced by IRbeta knockdown (siRNA). As in schizophrenia, the IRbeta knockdown cells demonstrated a reduction in the Akt content and activity. Total GSK-3 alpha/beta content remained unaltered, but phospho-Ser(21/9) GSK-3 alpha/beta levels were reduced indicating a net increase in the overall enzyme activity similar to that in schizophrenia. Insulin resistance phenotype was induced in mice by treatment with antipsychotic drug, clozapine. Behavioral testing showed decreases in startle response magnitude in animals treated with clozapine for 68 days. The treatment resulted in a functional inhibition of IRbeta but the Akt activation status remained unaltered. Changes in GSK-3 alpha/beta were consistent with a net decrease in the enzyme activity, as opposed to that in schizophrenia. The results suggest that alterations in insulin-dependent Akt signaling in schizophrenia are similar to those observed in our cellular but not animal models of insulin resistance. In animal model, clozapine ameliorates IRbeta deficits at the GSK-3 alpha/beta level, which may justify its role in treatment of schizophrenia. Our studies suggest that aberrant IR function may be important in the pathophysiology of schizophrenia.

Topics: Animals; Antibodies, Anti-Idiotypic; Antipsychotic Agents; Brain; Carrier Proteins; Clozapine; Diabetes Mellitus, Type 2; Disease Models, Animal; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Incidence; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Microfilament Proteins; Prefrontal Cortex; Proto-Oncogene Proteins c-akt; Receptor, Insulin; Reflex, Startle; Schizophrenia; Signal Transduction

Genetic and behavioral studies in humans and mouse mutants have implicated the gene encoding neuregulin-1 (Nrg-1) as a candidate susceptibility gene for schizophrenia. We examined the behavior of mice heterozygous for a mutation in neuregulin-1's immunoglobulin (Ig)-like domain (Ig-nrg-1 mice). We found that these animals displayed behaviors related to a schizophrenia-like phenotype, such as clozapine suppression of open-field and running wheel activity and impaired latent inhibition. Contrary to findings with other nrg-1 mutants, Ig-nrg-1 mice did not exhibit significantly elevated locomotion relative to littermate controls. These results suggest that Ig-Nrg-1's contribute to some - but not all - aspects of the schizophrenia-like phenotype of nrg-1 mutants, and further support nrg-1 as a candidate gene for schizophrenia.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Disease Models, Animal; Exploratory Behavior; Immunoglobulins; Mice; Mice, Mutant Strains; Motor Activity; Neural Inhibition; Neuregulin-1; Phenotype; Protein Structure, Tertiary; Running; Schizophrenia

Schizophrenia is characterized by disturbances in sensorimotor gating and attentional processes, which can be measured by prepulse inhibition (PPI) and latent inhibition (LI), respectively. Research has implicated dysfunction of neurotransmission at the NMDA-type glutamate receptor in this disorder.. This study was conducted to examine whether compounds that enhance NMDA receptor (NMDAR) activity via glycine B site, D-serine and ALX 5407 (glycine transporter type 1 inhibitor), alter PPI and LI in the presence or absence of an NMDAR antagonist, MK-801.. C57BL/6J mice were tested in a standard PPI paradigm with three prepulse intensities. LI was measured in a conditioned emotional response procedure by comparing suppression of drinking in response to a noise in mice that previously received 0 (non-preexposed) or 40 noise exposures (preexposed) followed by two or four noise-foot shock pairings.. Clozapine (3 mg/kg) and D-serine (600 mg/kg), but not ALX 5407, facilitated PPI. MK-801 dose dependently reduced PPI. The PPI disruptive effect of MK-801 (1 mg/kg) could be reversed by clozapine and ALX 5407, but not by D-serine. All the compounds were able to potentiate LI under conditions that disrupted LI in controls. MK-801 induced abnormal persistence of LI at a dose of 0.15 mg/kg. Clozapine, D-serine, and ALX 5407 were equally able to reverse persistent LI induced by MK-801.. D-Serine and ALX 5407 display similar effects to clozapine in PPI and LI mouse models, suggesting potential neuroleptic action. Moreover, the finding that agonists of NMDARs and clozapine can restore disrupted LI and disrupt persistent LI may point to a unique ability of the NMDA system to regulate negative and positive symptoms of schizophrenia.

Topics: Amino Acid Transport Systems, Neutral; Animals; Attention; Clozapine; Conditioning, Psychological; Disease Models, Animal; Dizocilpine Maleate; Glycine Plasma Membrane Transport Proteins; Male; Mice; Mice, Inbred C57BL; Receptors, N-Methyl-D-Aspartate; Schizophrenia; Serine

There is growing interest in detecting and treating schizophrenia during the "prodrome," before the symptoms are fully manifested. The objective of this study was to develop a putative model of the prodrome and study the effects of medications on it.. Rats were treated with different regimens of amphetamine to produce full sensitization (full syndrome) and partial sensitization (to model the prodromal state) and were then treated with typical and atypical antipsychotics and a D1 antagonist to mimic early intervention. After several weeks of withdrawal, locomotor activity in response to amphetamine and behavioral deficits (prepulse inhibition [PPI] and latent inhibition [LI]) were examined.. Animals that received the full sensitization showed significant increase in locomotor activity and a disruption in both PPI and LI. Animals treated with a partial regimen showed only a muted phenotype. The animals that received "early intervention" did not show progression from the prodromal to the full-blown phenotype.. The partial regimen of amphetamine injections provided a modified phenotype that could be regarded as a representative of the "prodromal" state. Early intervention, instituted once the prodromal state was already developed, prevented further progression into the full phenotype analogous to schizophrenia.

Topics: Amphetamine; Analysis of Variance; Animals; Antipsychotic Agents; Avoidance Learning; Behavior, Animal; Benzazepines; Central Nervous System Stimulants; Clozapine; Disease Models, Animal; Drug Administration Schedule; Drug Interactions; Haloperidol; Inhibition, Psychological; Male; Motor Activity; Neural Inhibition; Random Allocation; Rats; Rats, Sprague-Dawley; Reaction Time; Reflex, Startle; Schizophrenia; Substance Withdrawal Syndrome; Time Factors

Selective attention deficit, characterised by the inability to differentiate relevant from irrelevant information, is considered to underlie many cognitive deficits of schizophrenia, and appears to be only marginally responsive to treatment with current antipsychotics.. We compared the activity of the putative atypical antipsychotic SSR181507 (a dopamine D(2) receptor antagonist and 5HT(1A) receptor agonist) with reference compounds, on disturbances of novelty discrimination in a social context in rats, a behavioural paradigm that putatively models selective attention deficit.. A first (familiar) juvenile rat was presented to an adult rat for a period (P1) of 30 min. A second (novel) juvenile was then introduced at the end of P1 for a period (P2) of 5 min. The ability of the adult rat to discriminate between the two juveniles, presented at the same time, was evaluated by measuring the ratio of the time spent in interaction with the novel vs the familiar juvenile during P2.. Adult rats spent more time exploring the novel than the familiar juvenile. This novelty discrimination capacity was disrupted by: (1) parametric modification of the procedure (reduction of time spent in contact with the familiar juvenile during P1); (2) acute injection of psychotomimetics that are known to induce schizophrenia-like symptoms in humans, such as phencyclidine (PCP; 3 mg/kg, i.p.) and d-amphetamine (1 mg/kg, i.p.) and (3) neonatal treatment with PCP (three injections of 10 mg/kg, s.c.), a model based on the neurodevelopmental hypothesis of schizophrenia. The potential atypical antipsychotic SSR181507 (0.03-3 mg/kg, i.p.) and the atypical antipsychotics clozapine (0.1-1 mg/kg, i.p.) and amisulpride (1-3 mg/kg, i.p.) attenuated deficits in novelty discrimination produced by parametric manipulation and by acute or neonatal treatment with PCP. The typical antipsychotic haloperidol (up to 0.3 mg/kg, i.p.) attenuated only deficits in novelty discrimination produced by parametric modification.. Collectively, these results suggest that SSR181507 can alleviate disturbances of novelty discrimination in a social context in rats, and that this paradigm may represent a suitable animal model of selective attention deficits observed in schizophrenia.

Topics: Age Factors; Animals; Attention Deficit Disorder with Hyperactivity; Behavior, Animal; Clozapine; Dextroamphetamine; Dioxanes; Discrimination, Psychological; Disease Models, Animal; Dopamine Antagonists; Dopamine D2 Receptor Antagonists; Dose-Response Relationship, Drug; Female; Haloperidol; Humans; Imipramine; Injections, Intraperitoneal; Male; Phencyclidine; Rats; Rats, Wistar; Receptor, Serotonin, 5-HT1A; Receptors, Dopamine D2; Recognition, Psychology; Serotonin 5-HT1 Receptor Agonists; Serotonin Antagonists; Social Behavior; Tacrine; Tropanes

The alpha(2) adrenoceptor antagonist idazoxan enhances antipsychotic efficacy of classical dopamine D(2) antagonists in treatment-resistant schizophrenia. The mechanisms are not fully understood, but we have previously shown that the combination of idazoxan with the D(2/3) receptor antagonist raclopride, similarly to clozapine but not classical antipsychotic drugs, augments dopamine efflux in the prefrontal cortex, and also generates an enhanced suppression of the conditioned avoidance response. We have now investigated the effects of clozapine, raclopride, idazoxan and the combination of raclopride and idazoxan on (i) electrically evoked excitatory post-synaptic potentials and currents in pyramidal cells of the rat medial prefrontal cortex, using intracellular electrophysiological recording in vitro, (ii) the impaired cognitive function induced by the selective N-methyl-D-aspartate (NMDA) receptor antagonist MK-801, using the 8-arm radial maze test, (iii) the in-vivo D2, alpha(2A) and alpha(2C) receptor occupancies of these pharmacological treatments, using ex-vivo autoradiography. Whereas neither idazoxan nor raclopride alone had any effect, the combination exerted the same facilitation of glutamatergic transmission in rat prefrontal pyramidal neurons as clozapine, and this effect was found to be mediated by dopamine acting at D(1) receptors. Similarly to clozapine, the combination of idazoxan and raclopride also completely reversed the working-memory impairment in rats induced by MK-801. Moreover, these effects of the two treatment regimes were obtained at similar occupancies at D(2), alpha(2A) and alpha(2C) receptors respectively. Our results provide novel neurobiological and behavioural support for a pro-cognitive effect of adjunctive use of idazoxan with antipsychotic drugs that lack appreciable alpha(2) adrenoceptor-blocking properties, and define presynaptic alpha(2) adrenoceptors as major targets in antipsychotic drug development.

Topics: Adrenergic alpha-Antagonists; Animals; Behavior, Animal; Cerebral Cortex; Clozapine; Cognition Disorders; Disease Models, Animal; Dizocilpine Maleate; Dopamine D2 Receptor Antagonists; Dose-Response Relationship, Drug; Drug Interactions; Electric Stimulation; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Glutamic Acid; Idazoxan; In Vitro Techniques; Male; Maze Learning; Raclopride; Radioligand Assay; Rats; Rats, Sprague-Dawley; Rats, Wistar; Synaptic Transmission

Excessive activation of non-NMDA receptors, AMPA and kainate, contributes to neuronal degeneration in acute and progressive pathologies, possibly including schizophrenia. Because 5-HT(1A) receptor agonists have neuroprotective properties (e.g., against NMDA-induced neurotoxicity), we compared the effects of the antipsychotics, clozapine, ziprasidone and aripiprazole, that are partial agonists at 5-HT(1A) receptor, with those of haloperidol, which is devoid of 5-HT(1A) agonist properties, on kainic acid (KA)-induced striatal lesion volumes, in C57Bl/6N mice. The involvement of 5-HT(1A) receptors was determined by antagonist studies with WAY100635, and data were compared with those obtained using the potent and high efficacy 5-HT(1A) receptor agonist, F13714. Intra-striatal KA lesioning and measurement of lesion volumes using cresyl violet staining were carried out at 48 h after surgery. F13714, antipsychotics or vehicle were administered ip twice, 30 min before and 3 1/2 h after KA injection. WAY100635 (0.63 mg/kg) or vehicle were given sc 30 min before each drug injection. Clozapine (2 x 10 mg/kg), ziprasidone (2 x 20 mg/kg) and aripiprazole (2 x 10 mg/kg) decreased lesion volume by 61%, 59% and 73%, respectively. WAY100635 antagonized the effect of ziprasidone and of aripiprazole but only slightly attenuated that of clozapine. In contrast, haloperidol (2 x 0.16 mg/kg) did not affect KA-induced lesion volume. F13714 dose-dependently decreased lesion volume. The 61% decrease of lesion volume obtained with F13714 (2 x 0.63 mg/kg) was antagonized by WAY100635. WAY100635 alone did not affect lesion volume. These results show that 5-HT(1A) receptor activation protects against KA-induced striatal lesions and indicate that some atypical antipsychotic agents with 5-HT(1A) agonist properties may protect against excitotoxic injury, in vivo.

Topics: Aminopyridines; Animals; Antipsychotic Agents; Aripiprazole; Clozapine; Corpus Striatum; Disease Models, Animal; Excitatory Amino Acid Agonists; Haloperidol; Kainic Acid; Male; Mice; Mice, Inbred C57BL; Piperazines; Piperidines; Pyridines; Quinolones; Receptor, Serotonin, 5-HT1A; Schizophrenia; Serotonin 5-HT1 Receptor Agonists; Serotonin Antagonists; Thiazoles

A novel method of oral drug administration was used in a neuroleptic animal study. Seventy male Sprague-Dawley rats were randomly subdivided into four groups, which were treated with clozapine, haloperidol, diazepam or a vehicle solution (5% sucrose solution). Oral drug treatment was achieved by training the rats to drink the drug of choice mixed with five percent sucrose or vehicle solution from a syringe. Within 3-4 weeks the haloperidol group developed vacuous chewing movement, which did not disappear with discontinuation of the drug. Significant weight gain was observed for all drug groups in relation to the control group, whereas only the diazepam group showed a significant increase in response latency on the disengage test of sensorimotor function, which disappeared with drug withdrawal. A novel means of testing the motivational status showed that all drug-treated groups engaged in eating chocolate before grooming (t=11.69, p<0.001), whereas the control group showed no specific tendency towards either task. Furthermore, there was a significant delay in grooming for the haloperidol group compared to the other drug groups and controls. In conclusion, a novel method of oral drug administration with minimum stress was introduced that was sufficient to cause the described changes in behavioural parameters. Additionally, the combination of tests used provided an efficient discrimination between the behavioural effects of clozapine, haloperidol and diazepam in rodents.

Topics: Administration, Oral; Animals; Antipsychotic Agents; Behavior, Animal; Body Weight; Brain; Clozapine; Diazepam; Disease Models, Animal; Dyskinesia, Drug-Induced; Grooming; Haloperidol; Male; Mastication; Motivation; Motor Activity; Rats; Rats, Sprague-Dawley; Reaction Time

Human chromosome 22q11.2 has been implicated in various behavioral abnormalities, including schizophrenia and other neuropsychiatric/behavioral disorders. However, the specific genes within 22q11.2 that contribute to these disorders are still poorly understood. Here, we show that an approximately 200-kb segment of human 22q11.2 causes specific behavioral abnormalities in mice. Mice that overexpress an approximately 200-kb region of human 22q11.2, containing CDCrel, GP1Bbeta, TBX1, and WDR14, exhibited spontaneous sensitization of hyperactivity and a lack of habituation. These effects were ameliorated by antipsychotic drugs. The transgenic mice were also impaired in nesting behavior. Although Tbx1 has been shown to be responsible for many physical defects associated with 22q11.2 haploinsufficiency, Tbx1 heterozygous mice did not display these behavioral abnormalities. Our results show that the approximately 200-kb region of 22q11.2 contains a gene(s) responsible for behavioral abnormalities and suggest that distinct genetic components within 22q11.2 mediate physical and behavioral abnormalities.

Topics: Abnormalities, Multiple; Amphetamines; Animals; Antipsychotic Agents; Behavior, Animal; Chromosome Deletion; Chromosomes, Human, Pair 22; Clozapine; Disease Models, Animal; Female; Heterozygote; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Psychotic Disorders; Schizophrenia; Time Factors

A model of schizophrenia, the chakragati (ckr) mouse was serendipitously created as a result of a transgenic insertional mutation. The apparent loss-of-function of an endogenous gene produced mice that, when homozygous, displayed an abnormal circling behavior phenotype. To determine whether this phenotype could be corrected by atypical antipsychotics, we compared the effects of clozapine and olanzapine on rotational turns and hyperactivity. Both of these drugs successfully ameliorated circling behavior and hyperactivity in homozygous mice. The increased motor activity of these mutant mice was both qualitatively and quantitatively similar to that observed in wild-type animals treated with dizocilpine, an N-methyl-D-aspartate receptor antagonist that produces behaviors resembling positive symptoms of schizophrenia. Mice either homozygous or heterozygous for the mutation also displayed enlargement of the lateral ventricles, which was accompanied only in the homozygous genotype by a loss of individual myelinated axons in the striatum and agenesis of the corpus callosum. These structural brain deficits were selective in that the nigro-striatal dopamine system was normal in these homozygous mice. In addition, two types of interneurons in the neostriatum, namely those producing acetylcholine or nitric-oxide synthase were also devoid of significant structural abnormalities. These results indicate that the ckr mouse mutant could be used as a possible animal model to study the pathophysiology of schizophrenia and suggest possible strategies for treating the behavioral aspects of this brain disease.

Topics: Animals; Behavior, Animal; Benzodiazepines; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Female; Genetic Testing; Lateral Ventricles; Male; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Transgenic; Motor Activity; Mutation; Olanzapine; Renin; Schizophrenia

Prepulse inhibition (PPI) of acoustic startle is decreased in unmedicated schizophrenia patients and similar deficits can be induced in rats through pharmacological, environmental, or neuroanatomical manipulations. Recently, we reported that Brattleboro (BB) rats, a Long Evans (LE) strain with a single gene mutation, have inherent deficits in PPI homologous to those observed in schizophrenia patients. We also reported that PPI deficits in BB rats could be reversed by chronic but not acute administration of 0.5 mg/kg haloperidol. No other dose or drug was tested in that experiment. In this study, we tested the effects of acute subcutaneous administration of several doses of haloperidol as well as the second-generation antipsychotic, clozapine, and the putative novel antipsychotic, PD149163, a neurotensin mimetic that crosses the blood-brain barrier. Consistent with our previous report, BB rats exhibited PPI deficits compared to LE rats and none of the doses of haloperidol produced a significant effect on this PPI deficit. In contrast, 10 and 15 mg/kg of clozapine and all the doses of PD149163 tested reversed the PPI deficits in BB rats. In addition, haloperidol, but not clozapine or PD149163 produced significant catalepsy in BB rats, supporting the notion that PD149163 has a profile consistent with atypical antipsychotics and providing support for the predictive validity of the PPI results. These results further strengthen the notion that the BB rat is a useful predictive model of antipsychotic efficacy and suggest that this model may differentiate between antipsychotics belonging to different therapeutic categories, for example, first- and second-generation agents.

Topics: Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Gait Disorders, Neurologic; Haloperidol; Inhibition, Psychological; Male; Neurotensin; Rats; Rats, Brattleboro; Rats, Long-Evans; Reflex, Startle; Schizophrenia; Species Specificity

One of the most consistent findings in postmortem studies of schizophrenia is increased GABAA receptor binding and reduced glutamic acid decarboxylase (GAD67) expression. Due to long-term antipsychotic treatment before death, these findings may reflect not only the consequences of schizophrenia but also medication effects. To differentiate between these options, we used an animal model and evaluated long-term effects of typical (haloperidol) and atypical (clozapine) antipsychotic drugs on the GABAergic system. A total of 33 adult male rats were treated in three cohorts over a period of 6 months. One cohort of 11 animals received clozapine (45 mg/kg/day), another one received haloperidol (1.5 mg/kg/day) and a third one received pH-adapted minimal concentrations of HCl in the drinking water. Receptor autoradiography of the GABAA receptor ([3H]-muscimol binding) and in situ hybridization in adjacent sections with 35S-labeled cRNA probes of the y-aminobutyric acid (GABA)-producing enzyme, GAD67, was performed. While haloperidol increased GABAA receptor binding in striatum and nucleus accumbens (NA), it suppressed GABAA receptor binding in temporal (TEMPC) and parietal (PARC) cortex. Clozapine induced GABAA receptor binding in infralimbic cortex (ILC) and similar like haloperidol in anterior cingulate cortex (ACC), two regions of the limbic cortex. In addition, either drug increased gene expression of GAD67. It is concluded that antipsychotic drugs differentially alter the GABAergic system, strongly suggesting that drug effects are partially responsible for the up-regulation of GABAA receptor binding in certain brain regions as observed in postmortem brains of schizophrenic patients. However, the reduced GAD67 expression seen in postmortem brains does not appear to reflect drug effects, since our animal model demonstrated increased gene expression.

Topics: Animals; Antipsychotic Agents; Binding Sites; Clozapine; Disease Models, Animal; Drug Administration Schedule; Glutamate Decarboxylase; Haloperidol; Isoenzymes; Limbic System; Male; Parietal Lobe; Rats; Rats, Sprague-Dawley; Receptors, GABA-A; RNA, Complementary; Schizophrenia; Temporal Lobe; Up-Regulation

Insufficient inhibitory processing of the P50 auditory evoked potential (AEP) is observed in most schizophrenia patients and is not improved by typical antipsychotic drugs, such as haloperidol. This inhibitory processing deficit is associated with a subnormal level of hippocampal alpha7 nicotinic receptors (nAChRs), and drugs that activate these receptors normalize the deficit. The atypical antipsychotic clozapine also normalizes this deficit in schizophrenia patients, but by an unknown mechanism.. Similar to schizophrenia patients, DBA/2 mice spontaneously exhibit a deficit in inhibitory processing of the P20-N40 AEP, which is a rodent analogue of the human P50 AEP. The present study determined whether clozapine improved this deficit in DBA/2 mice, and by what mechanism.. Using a conditioning-testing paradigm with paired auditory stimuli to assess inhibitory P20-N40 AEP processing in DBA/2 mice, the effects of clozapine (0.1, 1, 3.33, or 10 mg/kg, i.p.) and haloperidol (1 mg/kg, i.p.) were assessed. The effect of clozapine (1 mg/kg) was assessed alone and after pre-administration of either alpha-bungarotoxin, an alpha7 nAChR antagonist, or dihydro-beta-erythroidine, an alpha4beta2 nAChR antagonist.. In a dose-dependent manner, clozapine improved the deficient inhibitory processing of the P20-N40 AEP normally exhibited by DBA/2 mice. Like alpha7 agonists, 1 mg/kg clozapine selectively increased the inhibition of the P20-N40 response to the second of paired auditory stimuli. The normalizing effect of 1 mg/kg clozapine was blocked by alpha-bungarotoxin, but not by dihydro-beta-erythroidine. Haloperidol did not improve DBA/2's deficient P20-N40 AEP processing.. Clozapine improved the deficient inhibitory processing of the P20-N40 AEP in DBA/2 mice, apparently through stimulation of alpha7 nicotinic receptors. This effect was not shared by the typical antipsychotic haloperidol.

Topics: Acoustic Stimulation; alpha7 Nicotinic Acetylcholine Receptor; Animals; Antipsychotic Agents; Auditory Perceptual Disorders; Bungarotoxins; Clozapine; Dihydro-beta-Erythroidine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Electroencephalography; Evoked Potentials, Auditory; Haloperidol; Hippocampus; Male; Mice; Mice, Inbred DBA; Nicotinic Antagonists; Receptors, Nicotinic; Time Factors

Topics: Animals; Antipsychotic Agents; Callithrix; Clozapine; Dibenzothiazepines; Disease Models, Animal; Dyskinesia, Drug-Induced; Humans; Quetiapine Fumarate; Schizophrenia; Schizophrenic Psychology; Treatment Outcome

Latent inhibition (LI) refers to retarded conditioning to a stimulus as a consequence of its inconsequential pre-exposure, and disrupted LI in the rat is considered to model an attentional deficit in schizophrenia. Blockade of NMDA receptor transmission, which produces behavioral effects potentially relevant to schizophrenic symptomatology in several animal models, has been reported to spare LI.. To show that systemic administration of the non-competitive NMDA antagonist MK-801 will lead to an abnormally persistent LI which will emerge under conditions that disrupt LI in controls, and that this will be reversed by the atypical neuroleptic clozapine but not by the typical neuroleptic haloperidol, as found for other NMDA antagonist-induced models.. LI was measured in a thirst-motivated conditioned emotional response (CER) procedure by comparing suppression of drinking in response to a tone in rats which previously received 0 (non-pre-exposed) or 40 tone exposures (pre-exposed) followed by two (experiment 1) or five (experiments 2-5) tone - foot shock pairings.. MK-801 at doses of 0.1 and 0.2 mg/kg reduced conditioned suppression while no effect on suppression was seen at the 0.05 mg/kg dose. At the latter dose, intact LI was seen with parameters that produced LI in controls (40 pre-exposures and two conditioning trials). Raising the number of conditioning trials to five disrupted LI in control rats, but MK-801-treated rats continued to show LI, and this abnormally persistent LI was due to the action of MK-801 in the conditioning stage. MK-801-induced LI perseveration was unaffected by both haloperidol (0.1 mg/kg) and clozapine (5 mg/kg) administered in conditioning, and was reversed by clozapine but not by haloperidol administered in pre-exposure.. MK-801-induced perseveration of LI is consistent with other reports of perseverative behaviors, suggested to be particularly relevant to negative symptoms of schizophrenia, following NMDA receptor blockade. We suggest that LI perseveration may model impaired attentional set shifting associated with negative symptoms of schizophrenia. Moreover, the finding that the action of MK-801 on LI and the action of clozapine are exerted in different stages of the LI procedure suggests that the MK-801-based LI model may provide a unique screening tool for the identification of novel antipsychotic compounds, whereby the schizophrenia-mimicking LI abnormality is drug-induced, but the detection of the antipsychotic action is not dependent on the mechanism of action of the pro-psychotic drug.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Conditioning, Psychological; Disease Models, Animal; Dizocilpine Maleate; Drinking Behavior; Haloperidol; Inhibition, Psychological; Male; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Schizophrenia; Schizophrenic Psychology

Latent inhibition (LI) refers to retarded conditioning to a stimulus as a consequence of its inconsequential preexposure. Amphetamine-induced disruption of LI and its potentiation by antipsychotic drugs (APDs) in the adult rat are well-established models of schizophrenia and antipsychotic drug action, respectively. It is not clear whether LI can be similarly modulated at prepubertal age.. In view of the notion that schizophrenia is a neurodevelopmental disorder whose overt expression depends on postpubertal brain maturational processes, we investigated whether several manipulations known to modulate LI in adult rats, including systemic administration of amphetamine and the atypical APD clozapine, are capable of producing the same effects in prepubertal (35-day-old) rats.. LI was measured in a thirst motivated conditioned emotional response (CER) procedure in which rats received 10 or 40 tone preexposures followed by 2 or 5 tone-footshock pairings.. Like in adults, LI was present with 40 preexposures and 2 conditioning trials. In contrast to findings in adults, LI was resistant to disruption by amphetamine at a dose (1 mg/kg) that significantly increased locomotor activity, as well as by reducing the number of preexposures to ten, increasing the number of conditioning trials to five, or changing the context between preexposure and conditioning. Clozapine (5 mg/kg) and the selective 5HT2A antagonist M100907 (0.3 mg/kg) administered in conditioning were without an effect on "persistent" LI with extended conditioning, but were capable of disrupting LI when administered in the preexposure stage, as found in adults.. The results point to functionality within brain systems regulating LI acquisition but not those regulating LI expression in periadolescent rats, further suggesting that postpubertal maturation of the latter systems may underlie schizophrenia-mimicking LI disruption reported in adult rats following perinatal manipulations and possibly disrupted LI observed in schizophrenia.

Topics: Aging; Amphetamine; Animals; Antipsychotic Agents; Behavior, Animal; Central Nervous System Stimulants; Clozapine; Conditioning, Classical; Disease Models, Animal; Drinking Behavior; Fluorobenzenes; Male; Models, Neurological; Movement; Neural Inhibition; Piperidines; Rats; Rats, Wistar; Schizophrenia; Time Factors

Prepulse inhibition (PPI) of the acoustic startle reflex is a measure of sensorimotor gating, which occurs across species and is deficient in severe neuropsychiatric disorders such as schizophrenia. In monkeys, as in rodents, phencyclidine (PCP) induces schizophrenia-like deficits in PPI. In rodents, in general, typical antipsychotics (e.g. haloperidol) reverse PPI deficits induced by dopamine (DA) agonists (e.g. apomorphine), but not those induced by N-methyl- d-aspartate (NMDA) receptor antagonists [e.g. phencyclidine (PCP)], whereas atypical antipsychotics (e.g. clozapine) reverse PPI deficits induced by DA agonists and NMDA antagonists. However, some discrepancies exist with some compounds and strains of rodents.. This study investigated whether a typical (haloperidol, 0.035 mg/kg) and an atypical (clozapine, 2.5 mg/kg) antipsychotic could be distinguished in their ability to reverse PCP-induced deficits in PPI in eight monkeys ( Cebus apella).. First, haloperidol dose was determined by its ability to attenuate apomorphine-induced deficits in PPI. Then, haloperidol and clozapine were tested in eight monkeys with PCP-induced deficits of PPI. Experimental parameters were similar to standard human PPI procedures, with 115 dB white noise startle pulses, either alone or preceded by 120 ms with a prepulse 16 dB above the 70 dB background noise.. Clozapine reversed PCP-induced PPI deficits. In contrast, haloperidol did not significantly attenuate PCP-induced PPI deficits even at doses that significantly attenuated apomorphine effects.. In this primate model, clozapine was distinguishable from haloperidol by its ability to attenuate PCP-induced deficits in PPI. The results provide further evidence that PPI in nonhuman primates may provide an important animal model for the development of novel anti-schizophrenia medications.

Topics: Acoustic Stimulation; Animals; Antipsychotic Agents; Behavior, Animal; Cebus; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Dyskinesias; Excitatory Amino Acid Antagonists; Female; Haloperidol; Neural Inhibition; Phencyclidine; Reflex, Startle; Schizophrenia

Prenatal exposure to infection is associated with increased liability to schizophrenia, and it is believed that such an association is mediated by the maternal immune response, in particular, the proinflammatory cytokines released by the maternal immune system, which may disrupt fetal brain development. Impaired capacity to ignore irrelevant stimuli is one of the central deficits in schizophrenia, and is manifested, among others, in loss of latent inhibition (LI), a phenomenon whereby repeated inconsequential pre-exposure to a stimulus impairs its subsequent capacity to signal significant consequences. We tested the effects of prenatal immune activation induced by peripheral administration of the synthetic cytokine releaser polyriboinosinic-polyribocytidilic acid (poly I : C) to pregnant dams, on LI in juvenile and adult offspring. Consistent with the characteristic maturational delay of schizophrenia, prenatal immune activation did not affect LI in the juvenile offspring, but led to LI disruption in adulthood. Both haloperidol (0.1 mg/kg) and clozapine (5 mg/kg) reinstated LI in the adult offspring. In addition, prenatal immune activation led to a postpubertal emergence of increased sensitivity to the locomotor-stimulating effects of amphetamine and increased in vitro striatal dopamine release, as well as to morphological alterations in the hippocampus and the entorhinal cortex in the adult offspring, consistent with the well-documented mesolimbic dopaminergic and temporolimbic pathology in schizophrenia. These results suggest that prenatal poly I : C administration may provide a neurodevelopmental model of schizophrenia that reproduces a putative inducing factor; mimics the temporal course as well as some central abnormalities of the disorder; and predicts responsiveness to antipsychotic drugs. Neuropsychopharmacology (2003) 28, 1778-1789. advance online publication, 16 July 2003; doi:10.1038/sj.npp.1300248

Topics: Aging; Amphetamine; Animals; Central Nervous System Stimulants; Clozapine; Corpus Striatum; Disease Models, Animal; Dopamine; Dopamine Antagonists; Drug Interactions; Female; GABA Antagonists; Haloperidol; Hippocampus; In Vitro Techniques; Inhibition, Psychological; Interferon Inducers; Male; Motor Activity; Poly I-C; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Wistar; Schizophrenia

Life-threatening hyperthermia occurs in some individuals taking 3,4-methylenedioxymethamphetamine (MDMA, ecstasy). In rabbits, sympathetically mediated vasoconstriction in heat-exchanging cutaneous beds (ear pinnae) contributes to MDMA-elicited hyperthermia. We investigated whether MDMA-elicited cutaneous vasoconstriction and hyperthermia are reversed by clozapine and olanzapine, atypical antipsychotic agents. Ear pinna blood flow and body temperature were measured in conscious rabbits; MDMA (6 mg/kg, i.v.) was administered; and clozapine (0.1-5 mg/kg, i.v.) or olanzapine (0.5 mg/kg, i.v.) was administered 15 min later. One hour after MDMA, temperature was 38.7 +/- 0.5 degrees C in 5 mg/kg clozapine-treated rabbits and 39.0 +/- 0.2 degrees C in olanzapine-treated rabbits, less than untreated animals (41.5 +/- 0.3 degrees C) and unchanged from pre-MDMA values. Ear pinna blood flow increased from the MDMA-induced near zero level within 5 min of clozapine or olanzapine administration. Clozapine-induced temperature and flow responses were dose-dependent. In urethane-anesthetized rabbits, MDMA (6 mg/kg, i.v.) increased ear pinna postganglionic sympathetic nerve discharge to 217 +/- 33% of the pre-MDMA baseline. Five minutes after clozapine (1 mg/kg, i.v.) discharge was reduced to 10 +/- 4% of the MDMA-elicited level. In conscious rats made hyperthermic by MDMA (10 mg/kg, s.c.), body temperature 1 hr after clozapine (3 mg/kg, s.c.) was 36.9 +/- 0.5 degrees C, <38.6 +/- 0.3 degrees C (Ringer's solution-treated) and not different from the pre-MDMA level. One hour after clozapine, rat tail blood flow was 24 +/- 3 cm/sec, greater than both flow in Ringer's solution-treated rats (8 +/- 1 cm/sec) and the pre-MDMA level (17 +/- 1 cm/sec). Clozapine and olanzapine, by interactions with 5-HT receptors or by other mechanisms, could reverse potentially fatal hyperthermia and cutaneous vasoconstriction occurring in some humans after ingestion of MDMA.

Topics: Anesthesia; Animals; Antipsychotic Agents; Benzodiazepines; Body Temperature; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Ear; Fever; N-Methyl-3,4-methylenedioxyamphetamine; Olanzapine; Pirenzepine; Rabbits; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Selective Serotonin Reuptake Inhibitors; Serotonin Antagonists; Skin; Sympathetic Nervous System; Tail; Treatment Outcome; Vasoconstriction; Wakefulness

Clozapine is a potent atypical neuroleptic or antipsychotic agent used to relieve symptoms of early-diagnosed schizophrenia. Aside from well-described dopamine and serotonin receptor blockade effects, clozapine may also be neuroprotective through its modulation of the p75 neurotrophin receptor (p75(NTR)) and superoxide dismutase 1 (SOD1) expression. The death-signalling activities of both p75(NTR) and mutant SOD1 are implicated in motor neuron degeneration in humans and transgenic mice with amyotrophic lateral sclerosis (ALS). We therefore investigated the effects of clozapine in cell culture and mouse models of ALS. Clozapine dose-dependently inhibited full-length and cleaved p75(NTR) but not SOD1 protein expression in the motor neuron-like (NSC-34) cell line. Furthermore, low concentrations of clozapine protected NSC-34 cells from paraquat-mediated superoxide toxicity, nerve growth factor (NGF)-induced death signalling, and serum deprivation, whereas high concentrations potentiated death. Systemic thrice-weekly administration of low and high-dose clozapine to mutant superoxide dismutase 1 (SOD1(G93A)) mice produced differential effects on disease onset and survival. Low-dose treatment was associated with delayed locomotor impairment and death, compared to high-dose clozapine, which accelerated paralysis and mortality (P < 0.05). Increased death was not attributable to toxicity, as clozapine-induced agranulocytosis was not detected from blood analysis. High-dose clozapine, however, produced extrapyramidal symptoms in mice manifest by hindlimb rigidity, despite reducing spinal cord p75(NTR) levels overall. These results suggest that although clozapine may exert p75(NTR)-mediated neuroprotective activity in vitro, its profound antagonistic effects on dopaminergic and serotonergic systems in vivo at high doses may exacerbate the phenotype of transgenic ALS mice.

Topics: Amyotrophic Lateral Sclerosis; Animals; Cell Death; Cells, Cultured; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Gene Expression; Mice; Mice, Transgenic; Motor Neurons; Neuroprotective Agents; Receptor, Nerve Growth Factor; Receptors, Nerve Growth Factor; Signal Transduction; Superoxide Dismutase

Topics: Animals; Antipsychotic Agents; Benzodiazepines; Clozapine; Disease Models, Animal; Fever; Humans; N-Methyl-3,4-methylenedioxyamphetamine; Olanzapine; Serotonin Antagonists

Neonatal ventral hippocampal (NVH) lesions in rats have been shown to induce behavioral abnormalities at adulthood thought to simulate some aspects of positive, negative and cognitive deficits classically observed in schizophrenic patients. Such lesions induced a post-pubertal emergence of prepulse inhibition deficits reminiscent of the sensorimotor gating deficits observed in a large majority of schizophrenic patients. Here we have investigated the capacity of typical and atypical antipsychotics to reverse PPI deficits seen in NVH-lesioned rats. We show that three atypical antipsychotics (clozapine, olanzapine and risperidone) were able to reverse lesion-induced PPI deficits, in contrast to haloperidol, a classical neuroleptic. These results show that the NVH lesion model seems to be endowed with a fair predictive validity as, like in schizophrenic patients, PPI deficits in lesioned animals were reversed by atypical antipsychotics but not by the typical neuroleptic haloperidol.

Topics: Animals; Antipsychotic Agents; Benzodiazepines; Clozapine; Disease Models, Animal; Haloperidol; Hippocampus; Male; Olanzapine; Pirenzepine; Rats; Rats, Sprague-Dawley; Reflex, Startle; Reserpine; Schizophrenia

Striatal enlargement has been consistently reported in schizophrenics receiving chronic neuroleptic treatment although the results following atypical antipsychotic treatment have been equivocal. In order to disentangle patient illness from a possible drug effect on brain structure, young adult rats were administered either haloperidol, risperidone, clozapine, olanzapine, or vehicle daily for four or eight months via drinking water. Significant increases in caudate-putamen volumes were seen in animals receiving either haloperidol or clozapine when compared with control animals following eight months of drug administration. Conversely, olanzapine-treated animals showed significant decreases in caudate-putamen volumes when compared with control animals after eight months of drug. Thus, converging evidence indicates that the neuroplastic response of the striatum following neuroleptic exposure causes volumetric increases, whereas atypical antipsychotics affect the basal ganglia differentially. The current data suggests that such differential responses may be due to both the pharmacological properties and the relative doses of the atypical agents.

Topics: Animals; Antipsychotic Agents; Caudate Nucleus; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Haloperidol; Hypertrophy; Male; Neostriatum; Neuronal Plasticity; Neurons; Putamen; Rats; Rats, Sprague-Dawley; Risperidone; Schizophrenia; Time Factors

A new diaryl-methylene piperidine derivative, 2, displayed an atypical antipsychotic profile both in vitro and in vivo. The main pharmacological characteristics of this compound appears to reside in a more potent antagonism of the 5-HT2 serotonergic receptor than of the D2 dopaminergic receptor. This confirms that molecules displaying a D2/5-HT2 binding ratio < 1 possess clozapine-like antipsychotic activity.

Topics: Animals; Antipsychotic Agents; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Mice; Piperidines; Protein Binding; Psychomotor Agitation; Psychotic Disorders; Receptors, Dopamine D2; Receptors, Serotonin; Serotonin Antagonists

JL13 [5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5] benzoxazepine fumarate] is a substance with a close structural resemblance to clozapine. However, it is less sensitive to oxidation and may therefore have less hematological side effects. In the present study, JL13 was compared with clozapine and haloperidol in several animal models for schizophrenia. The paw test represents a screening model for antipsychotic drugs that can discriminate between drugs with extrapyramidal side effects and drugs without. Haloperidol increased both forelimb retraction time and hindlimb retraction time (HRT), whereas both clozapine and JL13 increased only HRT. In the prepulse inhibition paradigm, all three drugs reversed the apomorphine- and the amphetamine-induced disruption of prepulse inhibition. However, whereas haloperidol was equally effective against both dopaminergic drugs, JL13 and clozapine were more effective against amphetamine. Finally, only JL13 was able to increase prepulse inhibition in normal rats, whereas only clozapine reduced basal startle amplitude. Taken together, these data suggest that JL13 may be an effective antipsychotic drug, with a profile similar to clozapine.

Topics: Amphetamine; Animals; Antipsychotic Agents; Benzodiazepinones; Central Nervous System Stimulants; Clozapine; Disease Models, Animal; Drug Evaluation, Preclinical; Haloperidol; Locomotion; Male; Pyridines; Rats; Rats, Wistar; Reflex, Startle; Schizophrenia

To evaluate the effect of quetiapine fumarate in animal models of schizophrenia and its possibility to induce extrapyramidal side effects (EPSE).. The enhancement of immobility in a forced swimming test of mice induced by repeated treatment with phencyclidine and amphetamine swimming "normalization" test of mice were used as animal models of negative and positive symptoms of schizophrenia, respectively. The paw test of rats was used to evaluate the possibility by quetiapine fumarate to induce EPSE.. After treatment with phencyclidine (10 mg.kg-1.d-1, s.c., 14 d), the immobility time in the forced swimming test of mice was increased (P < 0.01). Quetiapine fumarate (20, 40, and 80 mg.kg-1, ig) and clozapine (10 and 30 mg.kg-1, ig) attenuated the enhanced immobility in the forced swimming test induced by repeated treatment with phencyclidine (P < 0.01), whereas haloperidol (0.3 and 1 mg.kg-1, ig) had no effect. In amphetamine swimming "normalization" test, quetiapine fumarate ameliorated the disorder induced by amphetamine in a dose-dependent manner. In paw test, quetiapine fumarate was much less effective in increasing the forelimb retraction time (FRT) than the hindlimb retraction time (HRT). The minimal effective dose (MED) of HRT (MEDHRT) and FRT (MEDFRT) of quetiapine fumarate was 20 mg.kg-1 and 100 mg.kg-1, respectively, and the ratio of MEDFRT to MEDHRT was 5.. The effects of quetiapine fumarate in these models indicated its clinical effect on schizophrenia with a reduced liability to produce EPSE.

Topics: Amphetamine; Animals; Antipsychotic Agents; Basal Ganglia Diseases; Clozapine; Disease Models, Animal; Female; Haloperidol; Immobilization; Male; Mice; Phencyclidine; Rats; Rats, Wistar; Schizophrenia; Schizophrenia, Paranoid

Neuroleptic primed Cebus apella monkeys have proven reliable in screening antipsychotics for extrapyramidal side effect (EPS) potential in humans, and the ratio EPS liability/antiamphetamine efficacy ["therapeutic index" (TI)] has fit well with clinical results.. 1) To find the TIs of one new (quetiapine), three potential [NNC 756 (dopamine (DA) D1 antagonist), NNC 22-0031 (alpha-1 adrenergic/5-HT2 serotonergic/DA D1 and D2 antagonist) and DOD 647 (DA D1 and D2 antagonist)] and three old antipsychotics (haloperidol, melperone and clozapine), 2) to test the model further and 3) to gain more insight as to clozapine's neuropharmacology.. Seven monkeys received haloperidol daily for 2 years; all were sensitized to dystonia. All drugs were given SC, in increasing doses until two animals had dystonia/other adverse effects (AE), and in decreasing doses with a fixed dose of dextroamphetamine producing motor unrest and stereotypies, to find the minimum significant antiamphetamine dose (AA). The ratio AE/AA = TI.. Excepting clozapine and DOD 647, all drugs induced dystonia. At 2-4 mg/kg, clozapine caused uncoordinated movements, myoclonic jerks and rough tremor; unlike dystonia, the syndrome was not alleviated but worsened by the anticholinergic, biperiden. DOD 647 up to 2 mg/kg had no adverse effects. The TIs of the new and potential antipsychotics were 3-5 versus 4 for clozapine and 1 for haloperidol and melperone, suggesting that like clozapine, these new drugs will not produce EPS at antipsychotic doses.

Topics: Amphetamine; Animals; Antipsychotic Agents; Cebus; Clozapine; Dextroamphetamine; Disease Models, Animal; Dopamine Agents; Dystonia; Female; Male; Motor Activity; Movement Disorders

N-methyl-D-aspartate receptors (NMDARs) represent a subclass of glutamate receptors that play a critical role in neuronal development and physiology. We report here the generation of mice expressing only 5% of normal levels of the essential NMDAR1 (NR1) subunit. Unlike NR1 null mice, these mice survive to adulthood and display behavioral abnormalities, including increased motor activity and stereotypy and deficits in social and sexual interactions. These behavioral alterations are similar to those observed in pharmacologically induced animal models of schizophrenia and can be ameliorated by treatment with haloperidol or clozapine, antipsychotic drugs that antagonize dopaminergic and serotonergic receptors. These findings support a model in which reduced NMDA receptor activity results in schizophrenic-like behavior and reveals how pharmacological manipulation of monoaminergic pathways can affect this phenotype.

Topics: Animals; Antipsychotic Agents; Antisocial Personality Disorder; Behavior, Animal; Calcium Signaling; Clozapine; Disease Models, Animal; Dizocilpine Maleate; Dopamine Antagonists; Excitatory Amino Acid Antagonists; Female; Glutamic Acid; Haloperidol; Male; Mice; Mice, Knockout; Motor Activity; Phencyclidine; Receptors, N-Methyl-D-Aspartate; Schizophrenic Psychology; Serotonin Antagonists; Sexual Behavior, Animal; Social Behavior; Stereotyped Behavior

The present study tested the effects of the typical neuroleptic haloperidol and an atypical neuroleptic clozapine on ventral hippocampus stimulation-induced disruption of prepulse inhibition (PPI). Bilateral infusions of 0.7 microg NMDA into the ventral hippocampus disrupted PPI. The impairment of PPI following the infusion was completely normalized 24 h after the infusion. This disruption of PPI was antagonized by clozapine (5.0 mg/kg), but not by haloperidol (0.2 mg/kg). Since disruption of PPI is considered to constitute an animal model of schizophrenia that is related to the deficit of sensorimotor gating observed in schizophrenic patients, these results suggest that PPI disruption induced by intra-ventral hippocampal infusions of NMDA may serve as an animal model for the selective detection of atypical antipsychotics.

Topics: Acoustic Stimulation; Animals; Antipsychotic Agents; Clozapine; Disease Models, Animal; Excitatory Amino Acid Antagonists; Haloperidol; Hippocampus; Infusions, Parenteral; Male; N-Methylaspartate; Rats; Rats, Wistar; Reflex, Startle

Rats received haloperidol (1.0 mg/kg i.p.) or clozapine (10 mg/kg i.p.), twice daily for 4 weeks: vacuous chewing--recorded 26 h after the final injection--similarly increased in both groups. Three h later, the rats were challenged with dopaminomimetics, and automatically recorded jaw movements were analysed. Both apomorphine and a mixture of D1 and D2 receptor agonists (SKF 38393 resp. quinpirole) increased jaw movements in haloperidol-treated, but not clozapine-treated rats; SKF 38393 or quinpirole remained ineffective, when given alone. A fixed dose of quinpirole together with increasing doses of SKF 38393, but not a fixed dose of SKF 38393 together with increasing doses of quinpirole, produced a dose-dependent increase in jaw movements in otherwise non-treated rats, suggesting that the noted haloperidol-induced increase was due to a shift in the D1-D2 receptor balance towards a predominance of D1 receptors. This study presents a new animal model of tardive dyskinesia with predictive validity, good reliability and, especially, great efficiency.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Apomorphine; Behavior, Animal; Clozapine; Disease Models, Animal; Dopamine; Dopamine Agonists; Dopamine Antagonists; Dyskinesia, Drug-Induced; Haloperidol; Jaw; Male; Mastication; Quinpirole; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Serotonin Antagonists

Antipsychotic drugs can inhibit the effects of phencyclidine (PCP) and d-amphetamine (AMPH) in many rodent tests, but the effects are usually seen at doses that also affect vehicle-treated control rats, suggesting that the inhibition may be nonspecific. This study will attempt to test the predictive validity of these models based on the clinical observations that antipsychotics are not fully effective until after 2-3 weeks of administration in patients and that patients do not relapse immediately following abrupt withdrawal of medication. Haloperidol and clozapine were tested in rats after daily administration for 3 and 21 days in combination with vehicle or PCP (2.0 mg/kg) in the social interaction test, and with vehicle or AMPH (0.5 mg/kg) in standard activity cages. To separate acute from more long-lasting effects on the central nervous system (CNS) haloperidol and clozapine were tested with a short (45 or 30 min depending upon test) and a long (22-24 h) pretreatment time. The results demonstrated that haloperidol and clozapine following both 3 and 21 days of administration at the short pretreatment time inhibited the activity of vehicle-, PCP-, and AMPH-treated rats, whereas neither drug had consistent effects in any group at the long pre-treatment time. The data suggest that antipsychotics only inhibit PCP- and AMPH-induced behaviors in rodents by an acute drug-drug interaction, whereas any long-term effects of antipsychotic drug administration on the CNS cannot be revealed by PCP and AMPH in rodents.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Clozapine; Dextroamphetamine; Disease Models, Animal; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Hallucinogens; Haloperidol; Male; Motor Activity; Phencyclidine; Predictive Value of Tests; Rats; Rats, Wistar; Schizophrenia; Social Behavior; Stereotyped Behavior

The effects of the psychotomimetic drug phencyclidine on the neurochemistry and function of the prefrontal cortex in vervet monkeys were investigated. Monkeys treated with phencyclidine twice a day for 14 days displayed performance deficits on a task that was sensitive to prefrontal cortex function; the deficits were ameliorated by the atypical antipsychotic drug clozapine. Repeated exposure to phencyclidine caused a reduction in both basal and evoked dopamine utilization in the dorsolateral prefrontal cortex, a brain region that has long been associated with cognitive function. Behavioral deficits and decreased dopamine utilization remained after phencyclidine treatment was stopped, an indication that these effects were not simply due to direct drug effects. The data suggest that repeated administration of phencyclidine in monkeys may be useful for studying psychiatric disorders associated with cognitive dysfunction and dopamine hypofunction in the prefrontal cortex, particularly schizophrenia.

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Chlorocebus aethiops; Clozapine; Cognition; Disease Models, Animal; Dopamine; Excitatory Amino Acid Antagonists; Humans; Phencyclidine; Prefrontal Cortex; Schizophrenia; Time Factors

Topics: Animals; Antipsychotic Agents; Behavior, Animal; Chlorocebus aethiops; Clozapine; Cognition; Disease Models, Animal; Dopamine; Excitatory Amino Acid Antagonists; Memory; Phencyclidine; Prefrontal Cortex; Schizophrenia; Schizophrenic Psychology

Latent inhibition (LI) refers to retarded conditioning to a stimulus that has been repeatedly presented without reinforcement. LI is impaired in schizophrenia patients and in rats treated with amphetamine. Neuroleptic drugs produce two effects in this test paradigm: antagonism of amphetamine-induced disruption of LI, and enhancement of LI when administered on their own. The present experiments tested the effects of the atypical neuroleptic, clozapine, on LI. The experiments used a conditioned emotional response procedure in rats licking for water, consisting of three stages: preexposure, in which the to-be-conditioned stimulus (tone) was repeatedly presented without reinforcement; conditioning, in which the preexposed stimulus was paired with reinforcement (foot shock); and test, in which LI was indexed by animals' degree of suppression of licking during tone presentation. In experiments 1 and 2, the effects of 5.0 and 10.0 mg/kg clozapine on LI were assessed following 20 or 10 tone preexposures, respectively. Experiments 3 and 4 used 40 preexposures and investigated antagonism of amphetamine-induced disruption of LI by 5.0 and 10.0 mg/kg clozapine, respectively. The results demonstrated that clozapine possesses a neuroleptic profile in the LI model, namely, it facilitates the development of LI and antagonizes amphetamine-induced disruption of LI.

Topics: Animals; Antipsychotic Agents; Association Learning; Attention; Clozapine; Conditioning, Classical; Dextroamphetamine; Disease Models, Animal; Dose-Response Relationship, Drug; Humans; Inhibition, Psychological; Male; Mental Recall; Rats; Rats, Wistar; Schizophrenia; Schizophrenic Psychology

Immobility induced by forced swimming is well known as an animal model of depression. To develop an animal model for the negative symptoms of schizophrenia, in particular, the depressive symptoms, the effect of phencyclidine (PCP) on immobility in the forced swimming test was investigated in mice, since PCP produces negative symptoms-like behavioral changes in humans. Repeated treatment with PCP (10 mg/kg/day, sc, once a day for 14 days) prolonged the immobility time in the forced swimming test 24 hr after the final injection compared with saline treatment; the effect was not obtained by single treatment with PCP (10 mg/kg), or by repeated treatment with methamphetamine (0.3 and 1 mg/kg/day, sc, once a day for 14 days). The enhancing effect of PCP on the immobility persisted for at least 21 days after the withdrawal of the drug. Desipramine (10 mg/kg, po) attenuated the immobility induced by the forced swimming in mice repeatedly treated with saline. The enhancing effect of PCP on the immobility was attenuated by risperidone (0.3 mg/kg), clozapine (3 and 10 mg/kg), and desipramine (20 and 50 mg/kg), whereas haloperidol (0.3 and 1 mg/kg) had no effect. These results suggest that the enhancement of immobility in the forced swimming test brought about by repeated PCP treatment could be used as a model of the negative symptoms, particularly the depression, of schizophrenia.

Topics: Animals; Antidepressive Agents, Tricyclic; Antipsychotic Agents; Clozapine; Desipramine; Disease Models, Animal; Humans; Immobilization; Mice; Phencyclidine; Risperidone; Schizophrenia; Swimming

The predictive validity of catalepsy as a rodent model for detecting the extrapyramidal side effects (EPS) of antipsychotic drugs was recently questioned when the novel antipsychotic savoxepine produced little catalepsy in rodents while producing significant EPS in schizophrenic patients. Because catalepsy is viewed as an important model for predicting EPS, we decided to re-evaluate the effects of savoxepine. Savoxepine, clozapine, haloperidol, olanzapine, ORG 5222, raclopride, and risperidone were examined in two tests for catalepsy (grid and bar tests) in male Sprague-Dawley rats. The ability to antagonize amphetamine-induced hypermotility was also examined, since this measure is believed to predict clinical efficacy. With the exception of clozapine, all drugs produced dose-dependent catalepsy in both tests. For each drug, the minimum effective dose for producing catalepsy was greater than or equal to the ED50 for antagonizing amphetamine-induced hyperactivity (defined as the dose producing a 50% reduction in hyperactivity). Clozapine resulted in the widest separation of effective doses in the catalepsy and activity models. Raclopride produced the next largest separation while the remaining drugs resulted in only a one- or two-fold dose separation between the two behavioral tests. The results with haloperidol and clozapine are consistent with the clinical effects of these drugs (severe versus mild EPS). The ratios of effective doses in catalepsy and activity for the remaining novel drugs are also consistent with preliminary clinical findings indicating some EPS with each of these compounds. Thus, catalepsy remains a suitable rodent model for detecting compounds with EPS liability in humans.

Topics: Amphetamine; Animals; Antipsychotic Agents; Catalepsy; Clozapine; Disease Models, Animal; Extrapyramidal Tracts; Locomotion; Male; Rats; Rats, Sprague-Dawley; Time Factors

Previous studies have shown that alpha 1-adrenoceptors, dopamine D1-like and 5-HT2A receptors play an important role in the effects of the atypical neuroleptic, clozapine, on the parameter modelling antipsychotic efficacy in the paw test. Therefore, it became of interest to investigate whether antagonism of all these receptors together would give rise to effects characteristic of clozapine. The effects of the combined administration of the alpha 1-adrenoceptor antagonist phenoxybenzamine, the dopamine D1 receptor antagonist, SCH 39166 (4-(4-chloro-3-methoxyphenyl)-1,2- dihydronaphthalene), and the 5-HT2A receptor antagonist, ketanserin, were therefore measured in the paw test. The present data show that all three drugs together, but not simply combinations of two out of three, produced a profile similar to that of clozapine: a significant increase in the parameter modelling antipsychotic efficacy and no change in the parameter modelling extrapyramidal side-effects.

Topics: Adrenergic alpha-1 Receptor Antagonists; Analysis of Variance; Animals; Benzazepines; Clozapine; Disease Models, Animal; Dopamine Antagonists; Drug Synergism; Forelimb; Hindlimb; Ketanserin; Male; Pain Measurement; Phenoxybenzamine; Rats; Rats, Wistar; Receptor, Serotonin, 5-HT2A; Receptors, Dopamine D1; Receptors, Serotonin

1. In rats, the atypical neuroleptic, clozapine, has been found to increase the hindlimb retraction time but not the forelimb retraction time, in the paw test. These parameters have predictive validity for the antipsychotic efficacy and extrapyramidal side-effects of drugs, respectively. The present study analysed to what extent drugs acting on adrenoceptors affect the behavioural effect of clozapine in the paw test. 2. The alpha 1-adrenoceptor agonist, ST 587 but not the peripherally working alpha 1-agonist, methoxamine, decreased the effect of clozapine on the hindlimb retraction time. The alpha 1-antagonist phenoxybenzamine increased this effect of clozapine, and blocked the effect of ST 587 on clozapine at low doses. Only the combination of phenoxybenzamine with clozapine produced an increase in forelimb retraction time. 3. The alpha 2-adrenoceptor agonist, clonidine, decreased the effect of clozapine on the hindlimb retraction time. This effect was neither antagonized by the alpha 2-antagonist rauwolscine nor by the alpha 1-antagonist phenoxybenzamine. Rauwolscine or the peripherally working alpha 2-antagonist L-659,066 did not influence the effect of clozapine on the hindlimb retraction time. The forelimb retraction time was not affected by any of the drug combinations. 4. In contrast to the beta 2-adrenoceptor agonist, clenbuterol, which was ineffective, the peripherally acting beta-agonist, (-)-isoprenaline, increased the effects of clozapine on the hindlimb retraction time. The beta-antagonist, (-)-propranolol as well as the peripherally acting beta-antagonist, nadolol decreased this effect of clozapine. Low doses of the peripherally acting beta 1-antagonist, atenolol, as well as low doses of the beta2-antagonist, ICI-118,551, decreased the effect of clozapine. A low dose of nadolol blocked the effect of (-)-isoprenaline on clozapine. Only the combination of clenbuterol with clozapine produced an increase in forelimb retraction time.5. It is concluded that blockade of central alpha l-adrenoceptors plays an important role in the effect of clozapine on the hindlimb retraction time. Furthermore, the effect of clozapine on the hindlimb retraction time is strongly modulated by peripheral beta 1- and/or beta 2-adrenoceptors. Given the predictive validity of the paw test, the presented data suggest that the alpha 1-adrenoceptor antagonist properties of clozapine are important for its therapeutic effects, but not for its lack of extrapyramidal side-effec

Topics: Adrenergic alpha-1 Receptor Agonists; Adrenergic alpha-1 Receptor Antagonists; Adrenergic alpha-2 Receptor Agonists; Adrenergic alpha-2 Receptor Antagonists; Adrenergic beta-Antagonists; Animals; Antipsychotic Agents; Basal Ganglia Diseases; Behavior, Animal; Central Nervous System; Clozapine; Disease Models, Animal; Drug Interactions; Male; Peripheral Nervous System; Rats; Rats, Wistar; Receptors, Adrenergic

Topics: Animals; Antipsychotic Agents; Clozapine; Dibenzothiepins; Disease Models, Animal; Haloperidol; Humans; Rats; Schizophrenia

The effects of the atypical neuroleptic clozapine were studied in an inbred line of Syrian golden hamsters with generalized dystonia, i.e. a frequent movement disorder in humans. The effects of clozapine were compared with those of the classical neuroleptic, haloperidol. Clozapine, 7.5-20 mg/kg i.p., potently reduced the severity of dystonic attacks in the mutant hamster model, but induced marked sedation at these doses. Lower doses were ineffective. Haloperidol, 0.5 mg/kg i.p., significantly reduced the severity of dystonia without marked sedation. The finding that clozapine possesses antidystonic potency similar to that of haloperidol in a genetic model of dystonia might suggest that this atypical neuroleptic is an effective alternative in the treatment of dystonic patients who respond to neuroleptics, particularly because of the clinical evidence that clozapine is almost devoid of extrapyramidal adverse effects.

Topics: Animals; Clozapine; Cricetinae; Disease Models, Animal; Dystonia; Female; Haloperidol; Male; Mesocricetus; Mutation

Prepulse inhibition (PPI) of the acoustic startle response is a measure of sensorimotor gating that is impaired in both schizophrenic patients and in rats treated with dopamine agonists. The disruption of PPI by the dopamine agonist apomorphine (APO) is reversed by antipsychotic agents, including the atypical antipsychotic clozapine. Across a range of compounds, the ability of antipsychotics to restore PPI in APO-treated rats correlates significantly with their clinical potency. Since few animal models predict antipsychotic potency for clozapine, we further characterized the effects of clozapine and the typical antipsychotic haloperidol on APO-disrupted and baseline PPI in rats. The APO-induced disruption of PPI caused by intense (15 dB over background) prepulses was reversed in a dose-dependent manner by both clozapine and haloperidol. When weak (1-5 dB over background) prepulses were used, clozapine and haloperidol increased baseline PPI in control animals. Both APO-disrupted and baseline PPI may be useful in screening both typical and atypical antipsychotic agents.

Topics: Animals; Apomorphine; Clozapine; Disease Models, Animal; Dose-Response Relationship, Drug; Habituation, Psychophysiologic; Haloperidol; Male; Rats; Rats, Sprague-Dawley; Reflex, Startle; Schizophrenic Psychology

Acute and late onset movement disorders frequently complicate the treatment of psychosis with typical neuroleptic drugs like haloperidol, but not with atypical neuroleptic drugs like clozapine. Although the neural mechanisms underlying neuroleptic-induced movement disorders remain unknown, alterations in basal ganglia function are likely involved. A potential role for the endogenous opiate peptides in neuroleptic-induced movement disorders is suggested by the immunocytochemical localization of met5-enkephalin (ME) in the striatopallidal projection pathway, and by the increased levels of ME measured by radioimmunoassay in the rat caudate-putamen nuclei (CPN) following haloperidol treatment. We sought to determine whether met5-enkephalin-like immunoreactivity (MELI) in terminal fields within globus pallidus and in perikarya in CPN was differentially altered in rats chronically treated with haloperidol or clozapine. Acrolein-fixed forebrain sections were collected from cohorts of adult rats receiving 21-day oral administration of haloperidol, clozapine, or water. Sections from the three treatment groups were collectively processed for immunocytochemical labeling using varying dilutions of ME antiserum and the avidin-biotin peroxidase method. In globus pallidus, densitometry measures revealed significantly increased levels of immunoperoxidase labeling for ME in haloperidol-treated, but not in clozapine-treated animals. In CPN, optical densitometry as well as cell counting measurements also showed a significant increase in MELI only in the haloperidol-treated group. These results support the concept that alterations in endogenous opiate peptides in basal ganglia may contribute to movement disorders seen in patients receiving typical neuroleptic drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Clozapine; Corpus Striatum; Disease Models, Animal; Drug Administration Schedule; Dyskinesia, Drug-Induced; Enkephalin, Methionine; Globus Pallidus; Haloperidol; Immunoenzyme Techniques; Immunohistochemistry; Male; Models, Neurological; Organ Specificity; Rats; Rats, Inbred Strains; Water

Rats were administered haloperidol, clozapine, raclopride, or no drug for either 28 days or 8 months and then withdrawn from drug treatment for 3 weeks. Oral movements were repeatedly recorded, both by a human observer and by a computerized video analysis system which determined mouth openings and closings, or computer-scored movelets (CSMs). Four weeks of neuroleptic administration produced no changes in CSMs in any drug-treated group. Long-term administration induced distinctively different patterns of oral activity in the three drug groups, both in number of CSMs and the form of these movements. The oral movements which developed in the haloperidol-treated rats fit a previously described syndrome of late-onset oral dyskinesias which increased upon drug withdrawal. The clozapine- and raclopride-treated rats did not show the increased oral movements seen in the haloperidol animals, but each exhibited uniquely different CSM characteristics compared to controls. The results from this rodent model imply that haloperidol, but not clozapine or raclopride, produces late-onset oral dyskinesias in rats that fit the pattern expected for tardive dyskinesia.

Topics: Animals; Behavior, Animal; Body Weight; Clozapine; Dibenzazepines; Disease Models, Animal; Drinking; Dyskinesia, Drug-Induced; Female; Fourier Analysis; Haloperidol; Raclopride; Rats; Rats, Inbred Strains; Salicylamides

The model of LSD-potentiated apomorphine hypermotility (LPAH) in rats in comparison to apomorphine-induced hypermotility (AH) was used to investigate typical and atypical neuroleptics by analyzing complete dose response curves. Haloperidol (0.06 mg/kg) induced a parallel shift to the right of both the AH and LPAH dose response curves indicating dopaminolytic properties without any serotonolytic effect. Chlorpromazine (0.5 mg/kg) caused a mixed inhibitory effect on the LPAH, whereas the AH was not affected, probably due to the variety of actions at different transmission systems. Clozapine (0.125 mg/kg) antagonized the LSD effect indicating serotonolytic properties, whereas an additive influence on the AH might be caused by its cholinolytic properties. Sulpiride (10 mg/kg) potentiated both the AH and the LPAH, probably due to presynaptic dopaminergic mechanisms. Two conclusions can be drawn: (1) The results agree with and support the idea of a serotonergic modulation of the (predominant) mesolimbic dopaminergic system in the induction of locomotor effects. (2) The model of LPAH is useful to clearly differentiate typical from atypical neuroleptics, and to obtain information whether there is a primary involvement of dopaminergic or serotonergic mechanisms.

Topics: Animals; Apomorphine; Chlorpromazine; Clozapine; Disease Models, Animal; Drug Antagonism; Haloperidol; Humans; Hyperkinesis; Lysergic Acid Diethylamide; Male; Motor Activity; Rats; Rats, Inbred Strains; Sulpiride

Topics: Animals; Carbachol; Catheterization; Clozapine; Corpus Striatum; Disease Models, Animal; Dyskinesia, Drug-Induced; Haloperidol; Huntington Disease; Hydrazines; Levodopa; Male; Phentolamine; Rats; Trifluoperazine; Tyramine

An experimental analysis of the psychotropic activity of Leponex (in a chronic experiment on II cats) in conditions of a group interaction depicted that the preparation processes a definite tranquillizing and antipsychotic effect. In conditions of zoosocial interactions this drug promotes disappearance of neurotic reactions and a resocialization of animals in the zoosocial ierarchy. In tranquillizing doses the preparation has an antihypertensive effect and prevents the development of a long-term tonic hypertension due to emotional stress.

Topics: Animals; Antipsychotic Agents; Cats; Clozapine; Diazepam; Dibenzazepines; Disease Models, Animal; Haloperidol; Humans; Mental Disorders; Neurotic Disorders; Psychotic Disorders; Social Behavior; Tranquilizing Agents

The present study has compared the abilities of clozapine, haloperidol, chlorpromazine and loxapine to induce dopamine (DA)-receptor hypersensitivity in rats, as measured by the apomorphine response after withdrawal of the antipsychotic drugs. Haloperidose during 1-2 weeks after withdrawal. Clozapine, given prior to apomorphine, reduced the responses of the haloperidol and loxapine groups to the control level. The effects of haloperidol and clozapine were quantified in rats with unilateral striatal lesions. Biochemical investigations showed that tolerance developed to the increase in striatal homovanillic acid (HVA) after chronic treatment with haloperidol, chlorpromazine and loxapine, whereas clozapine (20 mg/kg p.o.) failed to affect the HVA content, and no tolerance developed to the increase seen at 80 mg/kg. Cross-tolerance to the rise in HVA was seen with haloperidol, chlorpromazine and loxapine, but chronicc pretreatment with clozapine failed to affect the rise in HVA induced by a singel dose of the former compounds.

Topics: Animals; Apomorphine; Chlorpromazine; Clozapine; Corpus Striatum; Dibenzazepines; Dibenzoxazepines; Disease Models, Animal; Dopamine; Drug Tolerance; Female; Haloperidol; Homovanillic Acid; Humans; Loxapine; Male; Movement Disorders; Rats; Receptors, Drug; Stereotyped Behavior; Substance Withdrawal Syndrome

According to Venables the span of psychotic processes extends from a low level of arousal with an increased reactivity toward sensory stimuli to a high level of arousal with a reduced reactivity toward sensory stimuli. The level of arousal and the degree of reactivity, or breadth of attention, are apparently controlled by a regulatory mechanism which increases the threshold for sensory input in threatening situations. Any factor producing an electroencephalographic arousal reaction leads to a narrowing of attention. Underestimation of the size of a given object is an expression of such a reduction in the span of attention. Various authors have found a reduction in size-constancy in schizophrenics, in particular in patients exhibiting a merkedly reduced contact with their environment. A model is described in which a strong sensory stimulus induces a state of immobilization in rats treated with a low dose of morphine. Electroencephalographic recordings show that the initial state of arousal induced by peripheral stimulation is replaced by high-amplitude slow-waves and spindles as the state of immobilization develops. The current results suggest that the sensory stimulation leads to excitation of the ascending reticular formation and via the Centrum medianum and the Nucleus centralis, to activation of the striatal system, resulting in catalepsy. It would thus appear that the reticular formation and the striatum alternate in excercising a control function over the state of arousal. This would be a logical way of limiting over-reaction, which can be demonstrated most simply on the motoric response. It seems justified, therefore, to assume a relationship between catatonic stupor and the immobilization induced by stimulation. This concept is supported by the observation that of all the compounds investigated only clozapine is capable of inhibiting the immobilization in the rat model. Clozapine is a powerful antipsychotic agent with a pronounced inhibitory effect both on the reticular arousal reaction and on the schizophrenic catatonia.

Topics: Animals; Arousal; Behavior, Animal; Catatonia; Clozapine; Disease Models, Animal; Humans; Rats; Schizophrenia