neuropeptide-y and Seizures

Anticonvulsant neuropeptides are best known for their ability to suppress seizures and modulate pain pathways. Galanin, neuropeptide Y, somatostatin, neurotensin, dynorphin, among others, have been validated as potential first-in-class anti-epileptic or/and analgesic compounds in animal models of epilepsy and pain, but their therapeutic potential extends to other neurological indications, including neurodegenerative and psychatric disorders. Disease-modifying properties of neuropeptides make them even more attractive templates for developing new-generation neurotherapeutics. Arguably, efforts to transform this class of neuropeptides into drugs have been limited compared to those for other bioactive peptides. Key challenges in developing neuropeptide-based anticonvulsants are: to engineer optimal receptor-subtype selectivity, to improve metabolic stability and to enhance their bioavailability, including penetration across the blood–brain barrier (BBB). Here, we summarize advances toward developing systemically active and CNS-penetrant neuropeptide analogs. Two main objectives of this review are: (1) to provide an overview of structural and pharmacological properties for selected anticonvulsant neuropeptides and their analogs and (2) to encourage broader efforts to convert these endogenous natural products into drug leads for pain, epilepsy and other neurological diseases.

Topics: Analgesics, Opioid; Anticonvulsants; Blood-Brain Barrier; Dynorphins; Epilepsy; Galanin; Molecular Structure; Nervous System Diseases; Neuropeptide Y; Neuropeptides; Neurotensin; Seizures; Sequence Homology, Amino Acid; Somatostatin

Topics: Animals; Central Nervous System Diseases; Emotions; Hippocampus; Humans; Neurodegenerative Diseases; Neuropeptide Y; Pain; Seizures; Stress, Psychological; Synapses

Nitric oxide (NO), a molecule with multidimensional effects has generated exponential amount of research since its identification as a biological messenger almost two decades back. The recent trend in NO research is to explore newer dimensions in the cellular and molecular mechanisms of actions and interactions of NO with various biomolecules and their implications in various pathophysiological states. Advances in our knowledge of the mechanisms by which this pleiotropic molecule regulates the expression of eukaryotic genes has generated considerable excitement and is paving the way for development of novel NO based therapeutic strategies. However, it is still a challenge to understand fully the paradox of beneficial and damaging effects of this exciting molecule. This review will discuss the current trends of research in this area especially highlighting the new insights gained from recent experimental and clinical studies. New approaches to reduce or augment the availability of NO to benefit a wide range of clinical conditions and avenues for future research are also briefly discussed.

Topics: Animals; Biomedical Research; Cell Adhesion Molecules; Cytokines; Estrogens; Gene Expression; Heat-Shock Proteins; Humans; Melatonin; Mitochondria; Natriuretic Peptides; Neoplasms; Neuroimmunomodulation; Neuronal Plasticity; Neuropeptide Y; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Opioid Peptides; Oxytocin; Seizures; Steroids; Stress, Physiological

In summary, NPY is clearly an important peptide in the adult rat dentate gyrus because it has the potential to influence synaptic transmission and neurogenesis. It may even have other functions, as yet undiscovered, mediated by glia or vasculature. The remarkable plasticity of NPY puts it in a position to allow dentate gyrus function to be modified in a changing environment. The importance of this plasticity in the context of epilepsy cannot be emphasized enough. It could help explain a range of observations about epilepsy that currently is poorly understood. For example, rapid increases in NPY could mediate postictal depression, the period of depression that can last for several hours after generalized seizures. It may mediate the "priming effect," which is a reduction in seizure threshold following an initial period of seizures. Finally, it could contribute to the resistance of dentate granule cells to degeneration after seizures. However, despite the focus in this review on seizure-induced changes, the changes described here also appear to occur after other types of manipulations, which considerably broadens the scope of NPY's role in the brain.

Topics: Animals; Cell Differentiation; Dentate Gyrus; Neuronal Plasticity; Neurons; Neuropeptide Y; Rats; Seizures; Synaptic Transmission

Prenatal administration of corticosteroids is common in obstetrics to improve the outcome of premature deliveries. Many pregnant women receive multiple corticosteroid courses. Long-term follow-up studies in humans are limited, but those available suggest detrimental effects on the behavior of those children. Animal data also show adverse effects of prenatal corticosteroids mainly in the hippocampus, a structure sensitive to corticosteroid action. Several molecules involved in neuronal survival, seizure susceptibility, and behavior have been identified as possible targets of prenatal corticosteroid effects. These molecules include hippocampal glucocorticoid receptors, brain-derived neurotrophic factor, corticotropin-releasing hormone, and neuropeptide Y. Prenatal corticosteroid treatment permanently reprograms expression of these molecules. The future goals of research in this area include development of specific antagonists of corticosteroid activation pathways that would help differentiate between positive main effects and undesired adverse effects of prenatally administered corticosteroids.

Topics: Adrenal Cortex Hormones; Animals; Brain-Derived Neurotrophic Factor; Cell Death; Corticotropin-Releasing Hormone; Disease Susceptibility; Female; Gene Expression Regulation; Hippocampus; Humans; Male; Neuropeptide Y; Pregnancy; Prenatal Exposure Delayed Effects; Receptors, Corticotropin-Releasing Hormone; Seizures

The endogenous NPY system in the brain is centrally involved in seizure regulation. The present paper reviews the evidence that exogenously applied NPY receptor ligands can inhibit epileptic seizures in various rodent in vitro and in vivo models. Agonists at Y2 and/or Y5 receptors and antagonists at Y1 receptors appear to inhibit seizures, depending on the seizure model studied. Although progress has been made, further studies are needed using transgenic animals as well as novel selective agonists and antagonists to firmly identify the NPY receptors mediating antiepileptic effects. This may lead to the development of future antiepileptic drug treatments targeting the NPY system.

Topics: Animals; Anticonvulsants; Brain; Electric Stimulation; Ligands; Neuropeptide Y; Receptors, Neuropeptide Y; Seizures

Neuropeptide Y (NPY) family of hormones exhibits a wide spectrum of central and peripheral activities mediated by six G-protein coupled receptor subtypes denoted as Y1, Y2, Y3, Y4, Y5, and y6. Investigations to date have implicated NPY in the pathophysiology of a number of diseases including feeding disorders, seizures, anxiety, diabetes, hypertension, congestive heart failure and intestinal disorders. These observations suggest that long-acting, potent NPY receptor selective agonists and antagonists developed could be used to treat a variety of diseases. These possibilities are discussed in this paper.

Topics: Feeding and Eating Disorders; Heart Failure; Humans; Malabsorption Syndromes; Neuropeptide Y; Receptors, Neuropeptide Y; Seizures

The high concentration of the tyrosine-rich polypeptide, neuropeptide Y (NPY), and the increase in the number of its receptor subtypes that have been characterized in the brain, raise the question of a functional role for NPY in the CNS. In addition to its peripheral actions on cardiovascular regulation, much attention has, therefore, been devoted to the CNS effects of NPY because of its stimulatory properties on food intake, its role in anxiolysis and its putative involvement in memory retention. Emerging evidence points to an important role for NPY in the regulation of neuronal activity both under physiological conditions and during pathological hyperactivity such as that which occurs during seizures. This article reviews recent studies that have shown the changes induced by seizures in the level and distribution of NPY, its receptor subtypes and their respective mRNAs in rat forebrain. Biochemical and electrophysiological findings in experimental models and tissue from human epilepsy sufferers suggest that NPY-mediated neurotransmission is altered by seizures. The pharmacological evidence and functional studies in NPY knockout mice highlight a crucial role for endogenous NPY, acting on different NPY receptors, in the control of seizures.

Topics: Animals; Hippocampus; Humans; Neuronal Plasticity; Neuropeptide Y; Receptors, Neuropeptide Y; Seizures

There has been direct evidence of gamma-aminobutyric acidA receptor modification during status epilepticus. Neuropeptides galanin and neuropeptide Y were demonstrated to play a role in terminating status epilepticus. Many of the CA3 pyramidal neurons destined to die as a consequence of status epilepticus were demonstrated to diminish expression of the GluR2 subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors. It was demonstrated that the pattern of cell loss due to status epilepticus is distinct in immature pups compared with adult rats. The genetic basis for susceptibility to neuronal loss during status epilepticus was described. There was increasing evidence of unique receptors and ion channels in the epileptic brain. The molecular studies of epileptic gamma-aminobutyric acidA receptors present on dentate granule cells of rats with temporal lobe epilepsy revealed altered gene and receptor expression before onset of recurrent spontaneous seizures. They also revealed insertion of new gamma-aminobutyric acidA receptors in the inhibitory synapses present on soma and proximal dendrites of dentate granule cells.

Topics: Animals; Cell Death; Epilepsy, Temporal Lobe; Galanin; Hippocampus; Humans; Neural Inhibition; Neurons; Neuropeptide Y; Receptors, GABA-A; Seizures; Status Epilepticus

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions, including learning and memory. In addition, experimental studies have suggested that NPY, together with its receptors, may have a direct implication in several pathological disorders, including epilepsy/seizure. NPY-like immunoreactivity and NPY receptors have been shown to be present throughout the brain, but is concentrated in the hippocampus. The hippocampal formation has been repeatedly implicated in the modulation of cognition, as well as the pathogenesis of seizure. This review will concentrate on the hippocampal distribution of NPY, its receptors and the putative role played by this peptide in seizure, together with the regulation of cognitive function associated with learning and memory.

Topics: Animals; Cognition; Hippocampus; Humans; Neuropeptide Y; Receptors, Neuropeptide Y; Seizures

Since its discovery in 1982, neuropeptide Y (NPY), a 36 amino-acid member of the pancreatic polypeptide family, has received considerable attention in the field of neuroscience. Originally isolated from porcine brain /86/, NPY is one of the most abundant and widely distributed peptides in the central nervous system. In the brain, NPY is present in the hypothalamus, limbic structures, cerebral cortex, brainstem and striatum /2,71/. Because of the widespread distribution of NPY, it has been implicated in the modulation of a variety of behaviors, including, but not limited to, circadian rhythms /1/, memory retention /33/, feeding /19,56/, sympathetic control of cardiovascular function /89/ and anxiety /42,43/. These functions have been reviewed elsewhere and will not be discussed in great detail here. The present review is intended to provide an overview of recent work implicating a role for NPY in limbic seizures.

Topics: Animals; Humans; Limbic System; Neuropeptide Y; Seizures

Topics: Animals; Epilepsy; Genetic Therapy; Hippocampus; Humans; Male; Neuropeptide Y; Rats; Rats, Wistar; Seizures; Serogroup

The evidence to guide clinicians regarding rationale polytherapy with current antiepileptic drugs (AEDs) is lacking, and current practice recommendations are largely empirical.  The excessive drug loading with combinatorial therapies of existing AEDs are associated with escalated neurotoxicity, and that emergence of pharmacoresistant seizures couldn't be averted. In pursuit of judicious selection of novel AEDs in combinatorial therapies with mechanism based evidences, standardized dose of raloxifene, fluoxetine, bromocriptine and their low dose combinations, were experimentally tested for their impact on maximal electroshock (MES) induced tonic hind limb extension (THLE) in mice. Hippocampal neuropeptide Y (NPY) levels, oxidative stress and histopathological studies were undertaken. The results suggest the potentiating effect of 4 mg/kg raloxifene on 14 mg/kg fluoxetine against MES induced THLE, as otherwise monotherapy with 4 mg/kg raloxifene was unable to produce an effect. The results also depicted better efficacy than carbamazepine (20 mg/kg), standard AED. Most profoundly, MES-induced significant (P < 0.001) reduction in hippocampal NPY levels, that were escalated insignificantly with the duo-drug combination, suggesting some other mechanism in mitigation of electroshock induced seizures. These results were later corroborated with assays to assess oxidative stress and neuronal damage. In conclusion, the results demonstrated the propitious therapeutic benefit of duo-drug low dose combination of drugs; raloxifene and fluoxetine, with diverse mode of actions fetching greater effectiveness in the management of generalized tonic clonic seizures (GTCS).

Topics: Animals; Anticonvulsants; Bromocriptine; Disease Models, Animal; Drug Synergism; Drug Therapy, Combination; Electroshock; Fluoxetine; Glutamic Acid; Hippocampus; Mice; Neuropeptide Y; Oxidative Stress; Raloxifene Hydrochloride; Receptors, Dopamine; Receptors, Serotonin; Seizures; Signal Transduction

The aim of our study to investigate clinical value of a set of neuropeptides (brain derived neurotrophic factor-BDNF, galanin and neuropeptide Y-NPY) in critically ill neonates. A total of 53 neonates (preterm: 26, term: 27) evaluated with lumbar pucture for etiologic evaluation were consequtively included into the study. Serum and CSF levels of the neuropeptides were measured in the first 48 h of life. All infants were prospectively followed for prognostic outcome (survival and neurodevelopmental) at the first year of life. The study cohort was categorized into four groups with respect to seizure development; preterm neonates with or without seizure and term neonates with or without seizure. Mean CSF levels of NPY (pg/ml) were significantly higher in term neonates with than those without seizures (389.76 vs. 122.66) and galanin (3.31 vs. 1.55) respectively. Term neonates with seizures had significantly higher serum levels of NPY (ng/mL) as compared with neonates without seizures (54.00 vs. 9.10). No significant difference was noted in serum and CSF levels for the set of neuropeptides in neonates with respect to prognostic outcome. Serum NPY and CSF NPY and galanin levels have a potential role for detection of clinical seizures in term neonates.

Topics: Biomarkers; Brain-Derived Neurotrophic Factor; Female; Galanin; Humans; Infant, Newborn; Infant, Premature; Male; Neuropeptide Y; Neuropeptides; Seizures

The full coding sequence of neuropeptide Y (NPY), prepro-NPY, is sequentially metabolized into three peptides; an N-terminus 28-amino acid signaling peptide, the NPY peptide itself (NPY1-36), and a 30-amino acid C-terminus peptide, known as the C-terminal flanking peptide of neuropeptide-Y (CPON). While the signaling peptide directs intracellular trafficking and NPY1-36 is well characterized, the biological function of CPON is unknown. This is noteworthy because CPON is co-stored and co-released along with NPY1-36 and could thus potentially serve important functions. To assess the role of CPON, we adapted a viral genetic approach using two different vector designs encoding NPY, but where the CPON coding sequence was excluded from one of the vectors. Thus, the effect of CPON was indirectly assessed. Male rats received intrahippocampal injections of either a vector encoding NPY1-39 whose metabolism yields NPY1-36 and not CPON, or a prepro-NPY vector encoding both NPY1-36 and CPON. A third vector encoding EGFP served as control. We subsequently studied to what extent CPON might affect seizure susceptibility and memory performance, respectively, to address two important questions to evaluate the potential of NPY gene therapy in epilepsy. Both NPY vectors, as compared to EGFP control, were found to be equally effective at suppressing acute kainate-induced seizures, and both did not influence learning and memory performance in the Morris water maze. Thus CPON itself does not appear to aid actions governed by vector-mediated overexpression of NPY1-36 within the hippocampus. Whether CPON serves other important functions remains to be determined.

Topics: Animals; Hippocampus; Male; Neuropeptide Y; Peptide Fragments; Protein Precursors; Rats; Rats, Wistar; Seizures; Spatial Learning; Spatial Memory

Epilepsy is marked by seizures that are a manifestation of excessive brain activity and is symptomatically treatable by anti-epileptic drugs (AEDs). Unfortunately, the older AEDs have many side effects, with cognitive impairment being a major side effect that affects the daily lives of people with epilepsy. Thus, this study aimed to determine if newer AEDs (Zonisamide, Levetiracetam, Perampanel, Lamotrigine and Valproic Acid) also cause cognitive impairment, using a zebrafish model. Acute seizures were induced in zebrafish using pentylenetetrazol (PTZ) and cognitive function was assessed using the T-maze test of learning and memory. Neurotransmitter and gene expression levels related to epilepsy as well as learning and memory were also studied to provide a better understanding of the underlying processes. Ultimately, impaired cognitive function was seen in AED treated zebrafish, regardless of whether seizures were induced. A highly significant decrease in γ-Aminobutyric Acid (GABA) and glutamate levels was also discovered, although acetylcholine levels were more variable. The gene expression levels of Brain-Derived Neurotrophic Factor (BDNF), Neuropeptide Y (NPY) and Cyclic Adenosine Monophosphate (CAMP) Responsive Element Binding Protein 1 (CREB-1) were not found to be significantly different in AED treated zebrafish. Based on the experimental results, a decrease in brain glutamate levels due to AED treatment appears to be at least one of the major factors behind the observed cognitive impairment in the treated zebrafish.

Topics: Acetylcholine; Animals; Anticonvulsants; Brain; Brain-Derived Neurotrophic Factor; Cognitive Dysfunction; Cyclic AMP; Cyclic AMP Response Element-Binding Protein; Drug Interactions; gamma-Aminobutyric Acid; Gene Expression; Glutamic Acid; Locomotion; Maze Learning; Neuropeptide Y; Pentylenetetrazole; Seizures; Zebrafish

Patients with psychogenic non-epileptic seizures (PNES) may present with convulsive events that are not accompanied by epileptiform brain activity. Video-electroencephalography (EEG) monitoring is the gold standard for diagnosis, yet not all patients experience convulsive episodes during video-EEG sessions. Hence, we aimed to construct a predictive model in order to detect PNES from serum hormone levels, detached from an evaluation of patients' convulsive episodes.. Fifteen female patients with PNES and 60 healthy female controls participated in the study, providing blood samples for hormone analysis. A binomial logistic regression model and the leave-one-out cross-validation were employed.. We found that levels of neuropeptide Y and adrenocorticotropic hormone were the optimal combination of predictors, with over 90% accuracy (area under the curve=0.980).. The ability to diagnose PNES irrespective of convulsive events would represent an important step considering its feasibility and affordability in daily clinical practice.

Topics: Adrenocorticotropic Hormone; Adult; Biomarkers; Case-Control Studies; Female; Humans; Neuropeptide Y; Predictive Value of Tests; Seizures; Young Adult

Neuropeptide Y (NPY) is an important 36 amino acid peptide that is abundantly expressed in the mammalian CNS and is known to be an endogenous modulator of seizure activity, including in rat models of Genetic Generalised Epilepsy (GGE) with absence seizures. Studies have shown that viral-mediated "gene therapy" with overexpression of NPY in the hippocampus can suppress seizures in acquired epilepsy animal models. This study investigated whether NPY gene delivery to the thalamus or somatosensory cortex, using recombinant adeno-associated viral vector (rAAV), could produce sustained seizure suppression in the GAERS model of GGE with absence seizures. Three cohorts of GAERS were injected bilaterally into the thalamus (short term n = 14 and long term n = 8) or the somatosensory cortex (n = 26) with rAAV-NPY or rAAV-empty. EEG recordings were acquired weekly post-treatment and seizure expression was quantified. Anxiety levels were tested using elevated plus maze and open field test. NPY and NPY receptor mRNA and protein expression were evaluated using quantitative PCR, immunohistochemistry and immunofluorescence. Viral overexpression of human NPY in the thalamus and somatosensory cortex in GAERS significantly reduced the time spent in seizure activity and number of seizures, whereas seizure duration was only reduced after thalamic NPY overexpression. Human and rat NPY and rat Y2 receptor mRNA expression was significantly increased in the somatosensory cortex. NPY overexpression in the thalamus was observed in rAAV-NPY treated rats compared to controls in the long term cohort. No effect was observed on anxiety behaviour. We conclude that virally-mediated human NPY overexpression in the thalamus or somatosensory cortex produces sustained anti-epileptic effects in GAERS. NPY gene therapy may represent a novel approach for the treatment of patients with genetic generalised epilepsies.

Topics: Animals; Disease Models, Animal; Epilepsy, Generalized; Gene Expression; Genetic Therapy; Male; Neuropeptide Y; Rats; Rats, Transgenic; Seizures

Psychogenic non-epileptic seizures (PNES) is a conversion disorder that reflects underlying psychological distress. Female patients with PNES often present with a history of prolonged stressors, especially sexual abuse. In the current study, we studied the relationship between neuropeptide Y (NPY) and PNES symptoms in women with a history of sexual abuse. NPY has been associated with resilience to stress and we hypothesized that low levels would increase the extent and severity of PNES symptoms in this patient population. Serum levels of NPY, and related hormones were measured in fifteen female PNES patients and sixty female controls. PNES patients reported more severe abuse histories, feeling of abandonment, and decreased perception of quality of life than controls. Importantly, they also had lower NPY levels. Our analysis indicates that low levels of NPY in PNES may confer greater vulnerability to exhibit seizure-like symptoms and lower quality of life.

Topics: Adrenocorticotropic Hormone; Adult; Case-Control Studies; Conversion Disorder; Disease Susceptibility; Electroencephalography; Estradiol; Female; Humans; Hydrocortisone; Neuropeptide Y; Oxytocin; Progesterone; Prolactin; Quality of Life; Resilience, Psychological; Seizures; Sex Offenses; Stress, Psychological; Testosterone; Young Adult

The objective of this study is to examine the effects of the endogenous ligands leptin, ghrelin, and neuropeptide Y (NPY) on seizure generation, the oxidant/antioxidant balance, and cytokine levels, which are a result of immune response in a convulsive seizure model. With this goal, Wistar rats were divided into 5 groups-Group 1: Saline, Group 2: Saline+PTZ (65mg/kg), Group 3: leptin (4mg/kg)+PTZ, Group 4: ghrelin (80μg/kg)+PTZ, and Group 5: NPY (60μg/kg)+PTZ. All injections were delivered intraperitoneally, and simultaneous electroencephalography (EEG) records were obtained. Seizure activity was scored by observing seizure behavior, and the onset time, latency, and seizure duration were determined according to the EEG records. At the end of the experiments, blood samples were obtained in all groups to assess the serum TNF-α, IL-1β, IL-6, FGF-2, galanin, nitric oxide (NOֹ), malondialdehyde (MDA), and glutathione (GSH) levels. The electrophysiological and biochemical findings (p<0.05) of this study show that all three peptides have anticonvulsant effects in the pentylenetetrazol (PTZ)-induced generalized tonic-clonic convulsive seizure model. The reduction of the levels of the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 caused by leptin, ghrelin, and NPY shows that these peptides may have anti-inflammatory effects in epileptic seizures. Also, leptin significantly increases the serum levels of the endogenous anticonvulsive agent galanin. The fact that each one of these endogenous peptides reduces the levels of MDA and increases the serum levels of GSH leads to the belief that they may have protective effects against oxidative damage that is thought to play a role in the pathogenesis of epilepsy. Our study contributes to the clarification of the role of these peptides in the brain in seizure-induced oxidative stress and immune system physiology and also presents new approaches to the etiology and treatment of tendency to epileptic seizures.

Topics: Animals; Cytokines; Disease Models, Animal; Fibroblast Growth Factor 2; Galanin; Ghrelin; Interleukin-1beta; Interleukin-6; Leptin; Malondialdehyde; Neuropeptide Y; Oxidative Stress; Pentylenetetrazole; Rats; Rats, Wistar; Seizures; Tumor Necrosis Factor-alpha

There is growing evidence that physical activity ameliorates the course of epilepsy in animal models as well as in clinical conditions. Since traumatic brain injury is one of the strongest determinants of epileptogenesis, the present study focuses on the question whether a moderate long-term physical training can decrease susceptibility to seizures evoked following brain damage. Wistar rats received a mechanical brain injury and were subjected to daily running sessions on a treadmill for 21 days. Thereafter, seizures were induced by pilocarpine injections in trained and non-trained, control groups. During the acute period of status epilepticus, the intensity of seizures was assessed within the six-hour observation period. The trained rats showed considerable amelioration of pilocarpine-induced motor symptoms when compared with their non-trained counterparts. Histological investigations of effects of the brain injury and of physical training detected significant quantitative changes in parvalbumin-, calretinin- and NPY-immunopositive neuronal populations. Some of the injury-induced changes, especially those shoved by parvalbumin-immunopositive neurons, were abolished by the subsequent physical training procedure and could, therefore, be considered as neuronal correlates of the observed functional amelioration of the injured brain.

Topics: Animals; Brain; Brain Injuries, Traumatic; Calbindin 2; Glial Fibrillary Acidic Protein; Male; Neurons; Neuropeptide Y; Parvalbumins; Physical Conditioning, Animal; Pilocarpine; Rats; Rats, Wistar; Seizures; Status Epilepticus

The efficiency of most of the new antiepileptic drugs (AEDs) on clinical trials still falls short the success reported in pre-clinical studies, possibly because the validity of the animal models is insufficient to fully represent the human pathology. To improve the translational value for testing AEDs, we propose the use of non-human primates. Here, we suggest that triggering limbic seizures with low doses of PTZ in pilocarpine-treated marmosets might provide a more effective basis for the development of AED. Marmosets with epileptic background were more susceptible to seizures induced by PTZ, which were at least 3 times longer and more severe (about 6 times greater frequency of generalized seizures) in comparison to naïve peers. Accordingly, PTZ-induced seizures were remarkably less attenuated by AEDs in epileptic than naïve marmosets. While phenobarbital (40mg/kg) virtually abolished seizures regardless of the animal's background, carbamazepine (120mg/kg) and valproic acid (400mg/kg) could not prevent PTZ-induced seizures in epileptic animals with the same efficiency as observed in naïve peers. VPA was less effective regarding the duration of individual seizures in epileptic animals, as assessed in ECoG (p=0.05). Similarly following CBZ treatment, the behavioral manifestation of generalized seizures lasted longer in epileptic (p<0.05), which were also more frequent than in the naïve group (p<0.05). As expected, epileptic marmosets experiencing stronger seizures showed more NPY- and ΔFosB-immunostained neurons in a number of brain areas associated with the generation and spread of limbic seizures. Our results suggest that PTZ induced seizures over an already existing epileptic background constitutes a reliable and controllable mean for the screening of new AEDs.

Topics: Animals; Anticonvulsants; Brain; Callithrix; Carbamazepine; Chronic Disease; Disease Models, Animal; Electrocorticography; Epilepsy; Female; Immunohistochemistry; Male; Neuropeptide Y; Pentylenetetrazole; Phenobarbital; Pilocarpine; Proto-Oncogene Proteins c-fos; Seizures; Valproic Acid

Cortical and hippocampal hypersynchrony of neuronal networks seems to be an early event in Alzheimer's disease pathogenesis. Many mouse models of the disease also present neuronal network hypersynchrony, as evidenced by higher susceptibility to pharmacologically-induced seizures, electroencephalographic seizures accompanied by spontaneous interictal spikes and expression of markers of chronic seizures such as neuropeptide Y ectopic expression in mossy fibers. This network hypersynchrony is thought to contribute to memory deficits, but whether it precedes the onset of memory deficits or not in mouse models remains unknown. The earliest memory impairments in the Tg2576 mouse model of Alzheimer's disease have been observed at 3 months of age. We thus assessed network hypersynchrony in Tg2576 and non-transgenic male mice at 1.5, 3 and 6 months of age. As soon as 1.5 months of age, Tg2576 mice presented higher seizure susceptibility to systemic injection of a GABAA receptor antagonist. They also displayed spontaneous interictal spikes on EEG recordings. Some Tg2576 mice presented hippocampal ectopic expression of neuropeptide Y which incidence seems to increase with age among the Tg2576 population. Our data reveal that network hypersynchrony appears very early in Tg2576 mice, before any demonstrated memory impairments.

Topics: Age Factors; Alzheimer Disease; Analysis of Variance; Animals; Biomarkers; Electroencephalography; Electroencephalography Phase Synchronization; GABA-A Receptor Antagonists; Immunohistochemistry; Male; Mice; Mice, Transgenic; Nerve Net; Neuropeptide Y; Seizures

Breath-holding spells are common paroxysmal events in children. Although the spells have a benign prognosis in the long term, they may be complicated by loss of consciousness, tonic-clonic movements, and occasionally seizures. Hence, this study aimed to measure the levels of serum S-100B proteins and neuropeptide-Y in the blood of children who experience breath-holding spells.. The study groups consisted of 45 patients (13 females, 32 males) with breath-holding spells and a control group of 32 healthy individuals (12 females, 20 males). The serum S-100B levels were measured using commercially available ELISA kits. The neuropeptide-Y levels in the serum were measured with RayBio® Human/Mouse/Rat Neuropeptide Y ELISA kits.. The mean serum S-100B protein level of the breath-holding spells group was 56.38 ± 13.26 pg/mL, and of the control group, 48.53 ± 16.77 pg/mL. The mean neuropeptide-Y level was 62.29 ± 13.89 pg/mL in the breath-holding spells group and 58.24 ± 12.30 pg/mL in the control group. There were significant differences between the groups with respect to serum S-100B protein levels (p = 0.025), while there was no statistically significant difference in neuropeptide-Y levels between the breath-holding spells group and the control group (p = 0.192).. The findings of this study suggest that frequent and lengthy breath-holding may lead to the development of neuronal metabolic dysfunction or neuronal damage which is most likely related to hypoxia. In light of these findings, future studies should be conducted using biochemical and radiological imaging techniques to support these results.

Topics: Case-Control Studies; Child; Female; Humans; Hyperventilation; Hypoxia; Hypoxia, Brain; Male; Neuropeptide Y; Respiration; S100 Calcium Binding Protein beta Subunit; Seizures

Antiepileptic drug therapy, though beneficial for restraining seizures, cannot thwart status epilepticus (SE) induced neurodegeneration or down-stream detrimental changes. We investigated the efficacy of resveratrol (RESV) for preventing SE-induced neurodegeneration, abnormal neurogenesis, oxidative stress and inflammation in the hippocampus. We induced SE in young rats and treated with either vehicle or RESV, commencing an hour after SE induction and continuing every hour for three-hours on SE day and twice daily thereafter for 3 days. Seizures were terminated in both groups two-hours after SE with a diazepam injection. In contrast to the vehicle-treated group, the hippocampus of animals receiving RESV during and after SE presented no loss of glutamatergic neurons in hippocampal cell layers, diminished loss of inhibitory interneurons expressing parvalbumin, somatostatin and neuropeptide Y in the dentate gyrus, reduced aberrant neurogenesis with preservation of reelin + interneurons, lowered concentration of oxidative stress byproduct malondialdehyde and pro-inflammatory cytokine tumor necrosis factor-alpha, normalized expression of oxidative stress responsive genes and diminished numbers of activated microglia. Thus, 4 days of RESV treatment after SE is efficacious for thwarting glutamatergic neuron degeneration, alleviating interneuron loss and abnormal neurogenesis, and suppressing oxidative stress and inflammation. These results have implications for restraining SE-induced chronic temporal lobe epilepsy.

Topics: Animals; Behavior, Animal; Cell Adhesion Molecules, Neuronal; Cell Death; Cognition; Extracellular Matrix Proteins; GABAergic Neurons; Gene Expression Regulation; Hippocampus; Inflammation; Interneurons; Longevity; Male; Microglia; Nerve Degeneration; Nerve Tissue Proteins; Neurogenesis; Neuropeptide Y; Oxidative Stress; Parvalbumins; Rats, Inbred F344; Reelin Protein; Resveratrol; Seizures; Serine Endopeptidases; Somatostatin; Status Epilepticus; Stilbenes; Tumor Necrosis Factor-alpha

Kainate-induced seizures constitute a model of temporal lobe epilepsy where prominent changes are observed in the hippocampal neuropeptide Y (NPY) system. However, little is known about the functional state and signal transduction of the NPY receptor population resulting from kainate exposure. Thus, in this study, we explored functional NPY receptor activity in the mouse hippocampus and neocortex after kainate-induced seizures using NPY-stimulated [(35) S]GTPγS binding. Moreover, we also studied levels of [(125) I]-peptide YY (PYY) binding and NPY, Y1, Y2, and Y5 receptor mRNA in these kainate-treated mice. Functional NPY binding was unchanged up to 12 h post-kainate, but decreased significantly in all hippocampal regions after 24 h and 1 week. Similarly, a decrease in [(125) I]-PYY binding was found in the dentate gyrus (DG) 1 week post-kainate. However, at 2 h, 6 h, and 12 h, [(125) I]-PYY binding was increased in all regions, and in the CA1 also at 24 h post-kainate. NPY mRNA levels were prominently increased in hippocampal regions, reaching maximum at 12 and 24 h. Y1 and Y5 mRNA levels were lowered in the DG at 24 and 2 h, respectively, while Y2 mRNA levels were elevated at 24 h in the DG and CA3. This study confirms rat kainate studies by showing pronounced adaptive changes in the mouse hippocampus both with regard to NPY synthesis and NPY receptor synthesis and binding, which may contribute to regulating neuronal seizure susceptibility after kainate. However, the potential seizure-suppressant effects of increased NPY gene expression at late time points post-kainate could be attenuated by the novel finding of reduced NPY-receptor G-protein activation.

Topics: Animals; Autoradiography; Disease Models, Animal; Epilepsy, Temporal Lobe; Guanosine 5'-O-(3-Thiotriphosphate); Hippocampus; Kainic Acid; Male; Mice; Neocortex; Neuropeptide Y; Peptide YY; Receptors, Neuropeptide Y; RNA, Messenger; Seizures; Time Factors

The mechanisms by which valproate, one of the most widely prescribed anti-epileptic drugs, suppresses seizures have not been fully elucidated but may involve up-regulation of neuropeptide Y (NPY). We investigated the effects of valproate treatment in Genetic Absence Epilepsy Rats from Strasbourg (GAERS) on brain NPY mRNA expression and seizure control. GAERS were administered either valproate (42 mg.kg(-1) hr(-1)) or saline continuously for 5 days. Electroencephalograms were recorded for 24 hrs on treatment days 1, 3 and 5 and the percentage of time spent in seizure activity was analysed. NPY mRNA expression was measured in different brain regions using qPCR. Valproate treatment suppressed seizures by 80% in GAERS (p<0.05) and increased NPY mRNA expression in the thalamus (p<0.05) compared to saline treatment. These results demonstrate that long-term valproate treatment results in an upregulation of thalamic expression of NPY implicating this as a potential contributor to the mechanism by which valproate suppresses absence seizures.

Topics: Animals; Anticonvulsants; Brain; Epilepsy, Absence; Male; Neuropeptide Y; Rats; Rats, Wistar; Seizures; Up-Regulation; Valproic Acid

An early but transient decrease in oxygen availability occurs during experimentally induced seizures. Using pimonidazole, which probes hypoxic insults, we found that by increasing the duration of pilocarpine-induced status epilepticus (SE) from 30 to 120 min, counts of pimonidazole-immunoreactive neurons also increased (P < 0.01, 120 vs 60 and 30 min). All the animals exposed to SE were immunopositive to pimonidazole, but a different scenario emerged during epileptogenesis when a decrease in pimonidazole-immunostained cells occurred from 7 to 14 days, so that only 1 out of 4 rats presented with pimonidazole-immunopositive cells. Pimonidazole-immunoreactive cells robustly reappeared at 21 days post-SE induction when all animals (7 out of 7) had developed spontaneous recurrent seizures. Specific neuronal markers revealed that immunopositivity to pimonidazole was present in cells identified by neuropeptide Y (NPY) or somatostatin antibodies. At variance, neurons immunopositive to parvalbumin or cholecystokinin were not immunopositive to pimonidazole. Pimonidazole-immunopositive neurons expressed remarkable immunoreactivity to hypoxia-inducible factor 1α (HIF-1α). Interestingly, surgical samples obtained from pharmacoresistant patients showed neurons co-labeled by HIF-1α and NPY antibodies. These interneurons, along with parvalbumin-positive interneurons that were negative to HIF-1α, showed immunopositivity to markers of cell damage, such as high-mobility group box 1 in the cytoplasm and cleaved caspase-3 in the nucleus. These findings suggest that interneurons are continuously endangered in rodent and human epileptogenic tissue. The presence of hypoxia and cell damage markers in NPY interneurons of rats and patients presenting with recurrent seizures indicates a mechanism of selective vulnerability in a specific neuronal subpopulation.

Topics: Animals; Anticonvulsants; Biomarkers; Cell Hypoxia; Cerebral Cortex; Convulsants; Diazepam; Disease Progression; Drug Resistance; Epilepsy; HMGB1 Protein; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Interneurons; Male; Nerve Tissue Proteins; Neuropeptide Y; Nitroimidazoles; Parvalbumins; Pilocarpine; Rats; Rats, Sprague-Dawley; Recurrence; Seizures; Status Epilepticus

We recently demonstrated that recombinant adeno-associated viral vector-induced hippocampal overexpression of neuropeptide Y receptor, Y2, exerts a seizure-suppressant effect in kindling and kainate-induced models of epilepsy in rats. Interestingly, additional overexpression of neuropeptide Y in the hippocampus strengthened the seizure-suppressant effect of transgene Y2 receptors. Here we show for the first time that another neuropeptide Y receptor, Y5, can also be overexpressed in the hippocampus. However, unlike Y2 receptor overexpression, transgene Y5 receptors in the hippocampus had no effect on kainate-induced motor seizures in rats. However, combined overexpression of Y5 receptors and neuropeptide Y exerted prominent suppression of seizures. This seizure-suppressant effect of combination gene therapy with Y5 receptors and neuropeptide Y was significantly stronger as compared to neuropeptide Y overexpression alone. These results suggest that overexpression of Y5 receptors in combination with neuropeptide Y could be an alternative approach for more effective suppression of hippocampal seizures.

Topics: Animals; Hippocampus; Kainic Acid; Kindling, Neurologic; Male; Neurons; Neuropeptide Y; Rats; Rats, Transgenic; Rats, Wistar; Receptors, Neuropeptide Y; Seizures

Neuropeptide Y's (NPY) anticonvulsant effect is generally attributed to its inhibitory effect on glutamate release from presynaptic nerve terminals, which is nicely demonstrated in in vitro settings. To date no study has attempted to investigate the effect of NPY in vivo on extracellular (EC) glutamate levels thus, via intracerebral microdialysis, we determined NPY's effect on hippocampal glutamate concentrations in vivo, and consequently the involvement of Y(1) receptors to this effect. NPY or the Y(1) agonist D-His26-NPY was intrahippocampally administered in rats for 2h, during which the hippocampal glutamate dialysate levels were monitored. Pilocarpine was subsequently co-administered with NPY or D-His26-NPY to determine their effect on pilocarpine-induced limbic seizures. Unexpectedly we noted that intrahippocampal administration of NPY or D-His26-NPY increased glutamate dialysate levels in a reproducible manner. NPY attenuated pilocarpine induced seizures, whereas D-His26-NPY did not. To clarify the role of Y(1) receptors in NPY's glutamatergic effect, NPY was co-administered with the selective Y(1) antagonist BVD10. Hippocampal Y(1) receptor blockade prevented the NPY-induced increase in hippocampal glutamate, proving that this induced glutamate increase is clearly Y(1) receptor mediated. This is the first evidence that NPY enhances hippocampal EC glutamate overflow in vivo via hippocampal Y(1) receptors without interfering with or contributing to NPY's anticonvulsant effect. Whilst this finding contrasts with the supposed glutamatergic hypothesis for NPY in the hippocampus, it is of significance to further assist in deciphering NPY's mechanisms of action in in vivo settings.

Topics: Animals; Anticonvulsants; Glutamic Acid; Hippocampus; Male; Microdialysis; Neuropeptide Y; Pilocarpine; Rats; Rats, Wistar; Receptors, Neuropeptide Y; Seizures

Neuropeptide Y (NPY) has been implicated in anxiolytic- and antidepressant-like behaviour as well as seizure-suppressant effects in rodents. Although these effects appear to be predominantly mediated via other NPY receptors (Y1 and/or Y2), several studies have also indicated a role for Y5 receptors. Gene therapy using recombinant viral vectors to induce overexpression of NPY, Y1 or Y2 receptors in the hippocampus or amygdala has previously been shown to modulate emotional behaviour and seizures in rodents. The present study explored the potential effects of gene therapy with the Y5 receptor, by testing effects of recombinant adeno-associated viral vector (rAAV) encoding Y5 (rAAV-Y5) in anxiety- and depression-like behaviour as well as in kainate-induced seizures in adult mice. The rAAV-Y5 vector injected into the hippocampus and amygdala induced a pronounced and sustained increase in Y5 receptor mRNA expression and functional Y5 receptor binding, but no significant effects were found with regard to anxiety- and depression-like behaviours or seizure susceptibility. Instead, rAAV-mediated Y5 receptor transgene overexpression resulted in moderate hyperactivity in the open field test. These results do not support a potential role for single transgene overexpression of Y5 receptors for modulating anxiety-/depression-like behaviours or seizures in adult mice. Whether the induction of hyperactivity by rAAV-Y5 could be relevant for other conditions remains to be studied.

Topics: Amygdala; Animals; Anti-Anxiety Agents; Antidepressive Agents; Anxiety; Behavior, Animal; Depression; Genetic Therapy; Genetic Vectors; Hippocampus; Hyperkinesis; Male; Mice; Mice, Inbred BALB C; Neuropeptide Y; Receptors, Neuropeptide Y; Seizures

  Rapamycin (RAP) has certain antiepileptogenic features. However, it is unclear whether these effects can be explained by the anticonvulsant action of RAP, which has not been studied. To address this question, we tested potential anticonvulsant effects of RAP in immature and adult rats using different seizure models and treatment paradigms. In addition, we studied changes in the expression of neuropeptide Y (NPY) induced by RAP, which may serve as an indirect target of the RAP action..   A complex approach was adopted to evaluate the anticonvulsant potential of RAP: We used flurothyl-, pentylenetetrazole (PTZ)-, N-methyl-D-aspartate (NMDA)-, and kainic acid (KA)-induced seizures to test the effects of RAP using different pretreatment protocols in immature and adult rats. We also evaluated expression of NPY within the primary motor cortex, hippocampal CA1, and dentate gyrus (DG) after different pretreatments with RAP in immature rats..   We found the following: (1) RAP administered with short-term pretreatment paradigms has a weak anticonvulsant potential in the seizure models with compromised inhibition. (2) Lack of RAP efficacy correlates with decreased NPY expression in the cortex, CA1, and DG. Specifically in immature rats, a single dose of RAP (3 mg/kg) 4 or 24 h before seizure testing had anticonvulsant effects against PTZ-induced seizures. In the flurothyl seizure model only the 4-h pretreatment with RAP was anticonvulsant in the both age groups. Short-term pretreatments with RAP had no effects against NMDA- and KA-induced seizures tested in immature rats. Long-term pretreatments with RAP over 8 days did not show beneficial effect in all tested seizure models in developing rats. Moreover, the long-term pretreatment with RAP had a slight proconvulsant effect on KA-induced seizures. In immature rats, any lack of anticonvulsant effect (including proconvulsant effect of multiple doses of RAP) was associated with downregulation of NPY expression in the cortex and DG. In immature animals, after a single dose of RAP with 24 h delay, we found a decrease of NPY expression in DG, and CA1 as well..   Our data show weak age-, treatment paradigm-, and model-specific anticonvulsant effects of RAP as well as loss of those effects after long-term RAP pretreatment associated with downregulation of NPY expression. These findings suggest that RAP is a poor anticonvulsant and may have beneficial effects only against epileptogenesis. In addition, our data present new insights into mechanisms of RAP action on seizures indicating a possible connection between mammalian target of rapamycin (mTOR) signaling and NPY system.

Topics: Age Factors; Animals; Animals, Newborn; Anticonvulsants; Disease Models, Animal; Gene Expression Regulation; Male; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Seizures; Sirolimus; Treatment Outcome

Acute seizure (AS) activity in old age has an increased predisposition for evolving into temporal lobe epilepsy (TLE). Furthermore, spontaneous seizures and cognitive dysfunction after AS activity are often intense in the aged population than in young adults. This could be due to an increased vulnerability of inhibitory interneurons in the aged hippocampus to AS activity. We investigated this issue by comparing the survival of hippocampal GABA-ergic interneurons that contain the neuropeptide Y (NPY) or the calcium binding protein parvalbumin (PV) between young adult (5-months old) and aged (22-months old) F344 rats at 12 days after three-hours of AS activity. Graded intraperitoneal injections of the kainic acid (KA) induced AS activity and a diazepam injection at 3 hours after the onset terminated AS-activity. Measurement of interneuron numbers in different hippocampal subfields revealed that NPY+ interneurons were relatively resistant to AS activity in the aged hippocampus in comparison to the young adult hippocampus. Whereas, PV+ interneurons were highly susceptible to AS activity in both age groups. However, as aging alone substantially depleted these populations, the aged hippocampus after three-hours of AS activity exhibited 48% reductions in NPY+ interneurons and 70% reductions in PV+ interneurons, in comparison to the young hippocampus after similar AS activity. Thus, AS activity-induced TLE in old age is associated with far fewer hippocampal NPY+ and PV+ interneuron numbers than AS-induced TLE in the young adult age. This discrepancy likely underlies the severe spontaneous seizures and cognitive dysfunction observed in the aged people after AS activity.

Topics: Aging; Animals; Epilepsy, Temporal Lobe; Hippocampus; Immunohistochemistry; In Vitro Techniques; Interneurons; Neuropeptide Y; Parvalbumins; Rats; Rats, Inbred F344; Seizures

The aim of this study was to analyze the expression of survival-related molecules such Akt and integrin-linked kinase (ILK) to evaluate Akt pathway activation in epileptogenesis process. Furthermore, was also investigated the mRNA expression of neuropeptide Y, a considered antiepileptic neuropeptide, in the pilocarpine-induced epilepsy. Male Wistar rats were submitted to the pilocarpine model of epilepsy. Hippocampi were removed 6h (acute phase), 12h (late acute), 5d (silent) and 60d (chronic) after status epilepticus (SE) onset, and from animals that received pilocarpine but did not develop SE (partial group). Hippocampi collected were used to specify mRNA expression using Real-Time PCR. Immunohistochemistry assay was employed to place ILK distribution in the hippocampus and Western blot technique was used to determine Akt activation level. A decrease in ILK mRNA content was found during acute (0.39+/-0.03) and chronic (0.48+/-0.06) periods when compared to control group (0.87+/-0.10). Protein levels of ILK were also diminished during both periods. Partial group showed increased ILK mRNA expression (0.80+/-0.06) when compared with animals in the acute stage. Silent group had ILK mRNA and immunoreactivity similar to control group. Western blot assay showed an augmentation in Akt activation in silent period (0.52+/-0.03) in comparison with control group (0.44+/-0.01). Neuropeptide Y mRNA expression increased in the partial group (1.67+/-0.22) and in the silent phase (1.45+/-0.29) when compared to control group (0.36+/-0.12). Results suggest that neuropeptide Y (as anticonvulsant) might act in protective mechanisms occurred during epileptic phenomena. Together with ILK expression and Akt activation, these molecules could be involved in hippocampal neuroprotection in epilepsy.

Topics: Analysis of Variance; Animals; Blotting, Western; Hippocampus; Immunohistochemistry; Male; Neuropeptide Y; Neuroprotective Agents; Phosphorylation; Pilocarpine; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Seizures; Signal Transduction; Status Epilepticus; Time Factors

Benzodiazepines (BDZ) have many effects on various kinds of epilepsies, but long-term treatment with BDZ often leads to drug tolerance. This study aimed to seek drugs which can reverse the tolerance of flurazepam (FZP), and to explore the role of neuropeptide Y (NPY) in the reversal effect.. A rat model of anticonvulsant tolerance to FZP was prepared. The rats with FZP tolerance were randomly assigned to seven groups: FZP-tolerance, and nifedipine, levetiracetam, topiramate, flumazenil, L-NAME and pyridoxamine treatment groups. The tolerance to FZP was evaluated through pentylenetetrazol (PTZ) infusion into a tail vein. The latency to onset of clonic seizure and the PTZ threshold were recorded. The mRNA of NPY receptor Y2 in the hippocampus was determined by RT-PCR, and the distribution of NPY in the hippocampus was examined by immunohistochemistry.. In comparison with the blank control group, the average latency to the onset of clonic seizure was shortened, the average PTZ threshold decreased and the expression of NYT and NPY receptor Y2 mRNA decreased significantly in the FZP-tolerance group (p<0.01). In comparison with the FZP-tolerance group, the average latency to onset of clonic seizure was prolonged by 2 times and the average PTZ threshold doubled in the topiramate treatment group. The average latency to onset of clonic seizure was prolonged by 1 time and the average PTZ threshold increased 1 time in the nifedipine, the levetiracetam and the flumazenil treatment groups. The mRNA expression of NPY receptor Y2 increased by 1 or 2 times in the flumazenil, the nifedipine and the topiramate treatment groups when compared with the FZP-tolerance group.. Nifedipine, levetiracetam, topiramate and flumazenil can reverse the anticonvulsant tolerance to flurazepam. NPY may play a role in mediating the reversal effect.

Topics: Animals; Anticonvulsants; Drug Tolerance; Flurazepam; Hippocampus; Male; Neuropeptide Y; Pentylenetetrazole; Rats; Rats, Sprague-Dawley; Reaction Time; Receptors, Neuropeptide Y; RNA, Messenger; Seizures

Neuropeptide Y (NPY) is an endogenous peptide with powerful anticonvulsant properties. Its overexpression in the rat hippocampus, mediated by the local application of recombinant adeno-associated viral (rAAV) vectors carrying the human NPY gene, results in significant reduction of seizures in acute and chronic seizure models. In this study, we characterized a more efficient rAAV-NPY vector to improve cell transfection in the injected area. The changes included pseudotyping with the AAV vector serotype 1 (rAAV1), and using the strong constitutive hybrid CBA promoter, which contains a cytomegalovirus enhancer and chicken beta-actin promoter sequences. We compared NPY expression and the associated anticonvulsant effects of this new vector, with those mediated by the former rAAV vector with chimeric serotype 1/2 (rAAV1/2). In addition, we investigated whether rAAV serotype 1 vector-mediated chronic NPY overexpression causes behavioural deficits that may detract from the clinical utility of this therapeutic approach. We report that rAAV-NPY serotype 1 vector has significantly improved anticonvulsant activity when compared with serotype 1/2 vector, as assessed by measuring EEG seizure activity in kainic acid treated rats. rAAV1-mediated NPY overexpression in naive rats did not result in alterations of physiological functions such as learning and memory, anxiety and locomotor activity. In addition, we did not observe glia activation, or humoral immune responses against serotype 1 vector, which could inactivate gene expression. Our findings show that rAAV1-NPY vector with the CBA promoter mediates powerful anticonvulsant effects and seems to be safe in rodents, thus it may be considered a vector of choice for possible clinical applications.

Topics: Actins; Animals; Dependovirus; Epilepsy, Temporal Lobe; Genetic Therapy; Genetic Vectors; Hippocampus; Immunity, Humoral; Kainic Acid; Learning; Male; Memory; Motor Activity; Neuropeptide Y; Promoter Regions, Genetic; Rats; Rats, Sprague-Dawley; Seizures; Transduction, Genetic

Brief, non-harmful seizures can activate endogenous protective programmes which render the brain resistant to damage caused by prolonged seizure episodes. Whether protection in epileptic tolerance is long-lasting or influences the subsequent development of epilepsy is uncertain. Presently, we investigated the relationship between hippocampal pathology, neuropeptide Y rearrangement and spontaneous seizures in sham- and seizure-preconditioned mice after status epilepticus induced by intra-amygdala kainate. Seizure-induced neuronal death at 24 h was significantly reduced in the ipsilateral hippocampal CA3 and hilus of tolerance mice compared to sham-preconditioned animals subject to status epilepticus. Damage to the CA3-hilus remained reduced in tolerance mice 21 days post-status. In sham-preconditioned mice subject to status epilepticus correlative statistics showed there was a strong inverse relationship between CA3, but not hilar, neuron counts and the number of spontaneous seizures. A strong positive association was also found between neuropeptide Y score and spontaneous seizure count in these mice. In contrast, there was no significant association between spontaneous seizure count and CA3 neuron loss or neuropeptide Y rearrangement in the tolerance mice. These data show that tolerance-conferred neuroprotection is long-lasting and that tolerance disrupts the normal association between CA3 damage, synaptic rearrangement and occurrence of spontaneous seizures in this model.

Topics: Amygdala; Animals; CA3 Region, Hippocampal; Cell Count; Cell Death; Cytoprotection; Kainic Acid; Male; Mice; Mice, Inbred C57BL; Mossy Fibers, Hippocampal; Neurons; Neuropeptide Y; Seizures; Status Epilepticus; Synapses; Time Factors

Seizure activity induces transient changes in the levels of neuropeptide Y (NPY) and somatostatin (SS) in various brain regions, but it remains unclear whether this effect can persist for long periods and whether it is relevant to epileptogenesis. We report that brief seizures evoked by electroshock produced an increase in the number of NPY neurons in the dentate hilus and retrosplenial cortex, an effect that lasted 10 weeks. The number of hilar SS neurons remained unchanged. However, the pentylenetetrazole seizure threshold was somewhat decreased in electroshock-treated rats. Despite this, no spontaneous seizures were detected in this group. In contrast, status epilepticus (pilocarpine model) produced loss of the hilar NPY and SS cells. Moreover, all rats with status epilepticus showed spontaneous behavioral seizures and their seizure threshold was markedly decreased. These findings support the notion that sustained NPY overexpression induced by brief seizures can be important in preventing epileptogenesis.

Topics: Animals; Cell Count; Cerebral Cortex; Disease Models, Animal; Electroshock; Gene Expression Regulation; Hippocampus; Male; Neurons; Neuropeptide Y; Pentylenetetrazole; Pilocarpine; Rats; Rats, Wistar; Seizures; Somatostatin

The p53 tumor suppressor is a multifunctional protein, which regulates cell cycle, differentiation, DNA repair and apoptosis. Experimental seizures up-regulate p53 in the brain, and acute seizure-induced neuronal death can be reduced by genetic deletion or pharmacologic inhibition of p53. However, few long-term functional consequences of p53 deficiency have been explored. Here, we investigated the development of epilepsy triggered by status epilepticus in wild-type and p53-deficient mice. Analysis of electroencephalogram (EEG) recordings during status epilepticus induced by intra-amygdala kainic acid (KA) showed that seizures lasted significantly longer in p53-deficient mice compared with wild-type animals. Nevertheless, neuronal death in the hippocampal CA3 subfield and the neocortex was significantly reduced at 72 h in p53-deficient mice. Long-term continuous EEG telemetry recordings after status epilepticus determined that the sum duration of spontaneous seizures was significantly longer in p53-deficient compared with wild-type mice. Hippocampal damage and neuropeptide Y distribution at the end of chronic recordings was found to be similar between p53-deficient and wild-type mice. The present study identifies protracted KA-induced electrographic status as a novel outcome of p53 deficiency and shows that the absence of p53 leads to an exacerbated epileptic phenotype. Accordingly, targeting p53 to protect against status epilepticus or related neurologic insults may be offset by deleterious consequences of reduced p53 function during epileptogenesis or in chronic epilepsy.

Topics: Animals; Apoptosis; CA3 Region, Hippocampal; Electroencephalography; Kainic Acid; Mice; Mice, Knockout; Neurons; Neuropeptide Y; Phenotype; Seizures; Status Epilepticus; Tumor Suppressor Protein p53

About one-third of women with epilepsy have a catamenial seizure pattern, in which seizures fluctuate with the menstrual cycle. Catamenial seizures occur more frequently when the ratio of circulating estradiol to progesterone is high, suggesting that estradiol is proconvulsant. We used adult female rats to test how estradiol-induced suppression of GABAergic inhibition in the hippocampus affects behavioral seizures induced by kainic acid. As expected, estradiol decreased the latency to initiate seizures, indicating increased seizure susceptibility. At the same time, however, estradiol also shortened the duration of late-stage seizures, indicating decreased seizure severity. Additional analyses showed that the decrease in seizure severity was attributable to greater release of the anticonvulsant neuropeptide, neuropeptide Y (NPY). First, blocking hippocampal NPY during seizures eliminated the estradiol-induced decrease in seizure duration. Second, light and electron microscopic studies indicated that estradiol increases the potentially releasable pool of NPY in inhibitory presynaptic boutons and facilitates the release of NPY from inhibitory boutons during seizures. Finally, the presence of estrogen receptor-alpha on large dense-core vesicles (LDCVs) in the hippocampus suggests that estradiol could facilitate neuropeptide release by acting directly on LDCVs themselves. Understanding how estradiol regulates NPY-containing LDCVs could point to molecular targets for novel anticonvulsant therapies.

Topics: Animals; Estradiol; Estrogen Receptor alpha; Female; Hippocampus; In Vitro Techniques; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Reaction Time; Secretory Vesicles; Seizures

We explored the effects of exogenous and endogenous erythropoietin (EPO) in a seizure model of rat. Adult male Fischer 344 rats received continuous intraventricular infusion of EPO dissolved in saline containing 1mg/ml of rat serum albumin, anti-EPO antibody, saline containing 1mg/ml of rat serum albumin or combined EPO and neuropeptide Y (NPY) Y2-receptor antagonist. Animals were behaviorally evaluated for seizure development over 6h after kainic acid injection followed by immunohistochemical assays. Mortality rate, seizure severity, apoptotic cell death and abnormal cell proliferation in the hippocampus of EPO-treated epileptic rats were significantly attenuated, compared to control rats. Anti-EPO antibody in non-EPO-treated animals worsened seizures and CA1 neuronal cell death, while NPY Y2-receptor antagonist cancelled the therapeutic effects of exogenous EPO. Both exogenous and endogenous EPO might modulate seizure severity and protect the hippocampal neurons in epileptic rats, via novel mechanistic pathways involving blockade of epileptogenic cell formation coupled with NPY receptor modulation in the hippocampus.

Topics: Animals; Apoptosis; Autoantibodies; CA1 Region, Hippocampal; Cell Proliferation; Dentate Gyrus; Disease Models, Animal; Erythropoietin; Hematopoiesis; Kainic Acid; Male; Neurons; Neuropeptide Y; Rats; Rats, Inbred F344; Receptors, Neuropeptide Y; Seizures; Severity of Illness Index; Signal Transduction; Up-Regulation

For many years, the ketogenic diet, including recent variants such the medium-chain triglyceride (MCT) diet, has been used with good clinical results in the management of refractory epilepsies, particularly in children. The antiepileptic effects of the diet, like the antiepileptic effects of starvation, have been attributed to accumulation of ketones, and there are experimental data in animal models to support this hypothesis. Recently, new data about the neuroendocrine response to the acute phase reaction (stress) have emerged, indicating involvement of various neuropeptides, including neuropeptide Y (NPY), which is considered as an endogenous anticonvulsant. The release of NPY is also stimulated by nutrients in the gut, particularly fats. Long-chain and, to a greater extent, medium-chain triglycerides, which are components of the ketogenic diet, stimulate NPY secretion. This effect may explain the improvement in seizure control after starvation, use of the classical ketogenic diet, and use of the MCT diet.

Topics: Anticonvulsants; Diet; Humans; Ketone Bodies; Neuropeptide Y; Nutrition Assessment; Seizures

We have shown that neuropeptide Y (NPY) regulates neurogenesis in the normal dentate gyrus (DG) via Y(1) receptors (Howell, O.W., Scharfman, H.E., Herzog, H., Sundstrom, L.E., Beck-Sickinger, A. and Gray, W.P. (2003) Neuropeptide Y is neuroproliferative for post-natal hippocampal precursor cells. J Neurochem, 86, 646-659; Howell, O.W., Doyle, K., Goodman, J.H., Scharfman, H.E., Herzog, H., Pringle, A., Beck-Sickinger, A.G. and Gray, W.P. (2005) Neuropeptide Y stimulates neuronal precursor proliferation in the post-natal and adult dentate gyrus. J Neurochem, 93, 560-570). This regulation may be relevant to epilepsy, because seizures increase both NPY expression and precursor cell proliferation in the DG. Therefore, the effects of NPY on DG precursors were evaluated in normal conditions and after status epilepticus. In addition, potentially distinct NPY-responsive precursors were identified, and an analysis performed not only of the DG, but also the caudal subventricular zone (cSVZ) and subcallosal zone (SCZ) where seizures modulate glial precursors. We show a proliferative effect of NPY on multipotent nestin cells expressing the stem cell marker Lewis-X from both the DG and the cSVZ/SCZ in vitro. We confirm an effect on proliferation in the cSVZ/SCZ of Y(1) receptor(-/-) mice and demonstrate a significant reduction in basal and seizure-induced proliferation in the DG of NPY(-/-) mice.

Topics: Animals; Antimetabolites; Bromodeoxyuridine; Cell Count; Cell Proliferation; Cells, Cultured; Dentate Gyrus; Hippocampus; Immunohistochemistry; Intermediate Filament Proteins; Male; Mice; Mice, Knockout; Nerve Tissue Proteins; Nestin; Neurons; Neuropeptide Y; Rats; Rats, Wistar; Seizures; Stem Cells; Tubulin

The dentate gyrus filters incoming activity into the hippocampus proper. It plays a role in learning and memory and in pathological states such as epilepsy. Some of hilar interneurons of the dentate gyrus express neuropeptide Y (NPY), which modulates granule cell activity. A subpopulation of the NPY-expressing inhibitory interneurons is sensitive to seizure-induced damage. Pretreatment with beta-estradiol in ovariectomized rats protects hilar interneurons against seizure-induced injury, including the NPY-containing damage-sensitive subpopulation. Here, we demonstrate that beta-estradiol enhances NPY expression within the hilar interneurons. In vitro paired-pulse stimulation of the mixed perforant path revealed beta-estradiol-induced augmentation of granule cell network inhibition, which at interstimulus intervals between 200 and 300 ms (corresponding to approximately 3-5 Hz) was NPY sensitive and involved Y1 receptors, whereas it was insensitive to GABA(B) or metabotropic glutamate receptor antagonists. Additionally, beta-estradiol pretreatment attenuated propagation of low-frequency (3.3 or 5 Hz) burst activity through the dentate gyrus. Scavenging endogenous NPY by intracerebroventricular administration of anti-NPY antibody accelerated kainic acid-induced seizure onset and increased seizure-induced neuronal damage in the hilus compared with rats treated with beta-estradiol alone. Together, we show that beta-estradiol upregulates hilar NPY and that this leads to enhancement in dentate gyrus inhibition of incoming frequencies between 3 and 5 Hz. Such frequencies are similar to the discharge frequencies recorded during seizure initiation in some patients with epilepsy. Thus, beta-estradiol-induced NPY-sensitive filtering of 3-5 Hz frequencies may be an important regulator of incoming seizure activity, but it could also serve a physiological purpose in modulating information flow into the hippocampus proper.

Topics: Animals; Dentate Gyrus; Estradiol; Female; Neural Inhibition; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Seizures

Stem cell niches exist around the lateral ventricle and in the subgranular layer of the dentate gyrus, supporting adult neurogenesis. Recently, a third germinal layer, the subcallosal zone has been identified supporting the generation of oligodendrocytes in the adult brain. We have previously described a proliferative role for neuropeptide Y on precursors in the dentate gyrus, caudal subventricular zone and subcallosal zone under basal conditions and in the dentate gyrus after seizures. Here we sought to determine a role for neuropeptide Y in seizure-induced proliferation in the subcallosal niche. Using the chemoconvulsant kainate and neuropeptide Y(-/-) mice with controls, we show an effect of neuropeptide Y on basal proliferation and demonstrate a significant reduction in seizure-induced proliferation in the subcallosal zone.

Topics: Analysis of Variance; Animals; Bromodeoxyuridine; Cell Count; Cell Proliferation; Hippocampus; Kainic Acid; Male; Mice; Mice, Knockout; Neurons; Neuropeptide Y; Organogenesis; Seizures

Hemimegalencephaly (HMEG) is a malformation of cortical development characterized by unilateral enlargement of the cerebral hemisphere, severe architectural and cellular abnormalities and association with intractable epilepsy. HMEG may represent an isolated lesion of the central nervous system, but may also be associated with several neurocutaneous syndromes. In the present study we discuss the neuropathological findings of two autopsy cases of HMEG associated with linear naevus sebaceous syndrome. Both cases showed the presence of linear naevus sebaceous on extensive areas of the face. The neurochemical profile of the glial and neuronal components in the affected hemisphere was determined using immunocytochemical markers and was compared with the unaffected contralateral hemisphere and normal control tissue. The observed cytomegalic neurones expressed receptors for distinct neurotransmitters, neuropeptides and growth factors. Analysis of components of the phosphoinositide 3-kinase pathway revealed expression of phospho-S6 ribosomal protein in cytomegalic neurones. Autopsy findings confirm the complexity of the histologic phenotypic manifestations in HMEG and proved useful in determining the spectrum of cytoarchitectural and neurochemical abnormalities, underlying the molecular pathogenesis and epileptogenesis of this brain malformation.

Topics: Adolescent; Autopsy; Brain Chemistry; Cell Count; Cerebral Cortex; Functional Laterality; Humans; Immunohistochemistry; Infant, Newborn; Male; Nerve Tissue Proteins; Neurons; Neuropeptide Y; Nevus; Receptors, Glutamate; Seizures; Syndrome; Tissue Fixation; Vascular Endothelial Growth Factor A

Neuropeptide Y (NPY) is a 36-amino-acid peptide that attenuates seizure activity following direct infusion or adeno-associated virus (AAV)-mediated expression in the central nervous system. However, NPY activates all NPY receptor subtypes, potentially causing unwanted side effects. NPY13-36 is a C-terminal peptide fragment of NPY that primarily activates the NPY Y2 receptor, thought to mediate the antiseizure activity. Therefore, we investigated if recombinant adeno-associated virus-mediated expression and constitutive secretion of NPY or NPY13-36 could alter limbic seizure sensitivity. Rats received bilateral piriform cortex infusions of AAV vectors that express and constitutively secrete full-length NPY (AAV-FIB-NPY) or NPY13-36 (AAV-FIB-NPY13-36). Control rats received no infusion, as we have previously shown that vectors expressing and secreting reporter genes like GFP (AAV-FIB-EGFP), as well as vectors expressing peptides that lack secretion sequences (AAV-GAL) have no effect on seizures. One week later, all animals received kainic acid (10 mg kg(-1), intraperitoneally), and the latencies to wet dog shakes and limbic seizure behaviors were determined. Although both control and vector-treated rats developed wet dog shake behaviors with similar latencies, the latencies to class III and class IV limbic seizures were significantly prolonged in both NPY- and NPY13-36-treated groups. Thus, AAV-mediated expression and constitutive secretion of NPY and NPY13-36 is effective in attenuating limbic seizures, and provides a platform for delivering therapeutic peptide fragments with increased receptor selectivity.

Topics: Animals; Dependovirus; Gene Expression; Genetic Therapy; Genetic Vectors; Hippocampus; Kainic Acid; Models, Animal; Neuropeptide Y; Peptide Fragments; Rats; Receptors, Neuropeptide Y; Seizures; Time Factors; Transduction, Genetic

The mechanisms by which electroconvulsive therapy (ECT) causes its antidepressive effect are unknown. Because ECT requires repeated induction of electroconvulsive seizures, adaptive changes in the brain and regulation of gene expression, are likely to be the fundamental basis on which ECT acts. Neuropeptide Y (NPY) gene expression is increased after multiple electroconvulsive stimulations (ECS) and since it also has anticonvulsant and antidepressant properties, it has led to the hypothesis that the beneficial effect of ECT is mediated via its activation of NPY-dependent neurotransmission. We have therefore examined in detail the temporal profile of NPY gene expression, using in situ hybridisation histochemistry in the rat dentate gyrus and piriform cortex - two brain areas centrally involved in seizure regulation. NPY mRNA in both regions was found to increase gradually with the number of ECS, reaching a maximum (550-700%) after approximately 14 ECS where no further increase was achieved by additional ECS. A number of 14 ECS was also shown to exert anticonvulsant activity against kainic acid seizures. In the dentate gyrus, repeated ECS also caused a gradual, but smaller, increase in the expression of somatostatin (SS) - a neuropeptide that is co-localised with NPY and also has anticonvulsant effects. These results shows that NPYergic and, to a lesser extent, SSergic neurotransmission is activated by ECS and support the hypothesis that these neuropeptides could play a central role in the anticonvulsant and antidepressant effect of ECT.

Topics: Animals; Dentate Gyrus; Electroconvulsive Therapy; Gene Expression; Hippocampus; In Situ Hybridization; Male; Neuropeptide Y; Periodicity; Rats; Rats, Wistar; Seizures; Somatostatin; Synaptic Transmission; Up-Regulation

The links among the extent of hippocampal neurodegeneration, the frequency of spontaneous recurrent motor seizures (SRMS), and the degree of aberrant mossy fiber sprouting (MFS) in temporal lobe epilepsy (TLE) are a subject of contention because of variable findings in different animal models and human studies. To understand these issues further, we quantified these parameters at 3-5 months after graded injections of low doses of kainic acid (KA) in adult F344 rats. KA was administered every 1 hr for 4 hr, for a cumulative dose of 10.5 mg/kg bw, to induce continuous stages III-V motor seizures for >3 hr. At 4 days post-KA, the majority of rats (77%) exhibited moderate bilateral neurodegeneration in different regions of the hippocampus; however, 23% of rats exhibited massive neurodegeneration in all hippocampal regions. All KA-treated rats displayed robust SRMS at 3 months post-KA, and the severity of SRMS increased over time. Analyses of surviving neurons at 5 months post-KA revealed two subgroups of rats, one with moderate hippocampal injury (HI; 55% of rats) and another with widespread HI (45%). Rats with widespread HI exhibited greater loss of CA3 pyramidal neurons and robust aberrant MFS than rats with moderate HI. However, the frequency of SRMS (approximately 3/hr) was comparable between rats with moderate and widespread HI. Thus, in comparison with TLE model using Sprague-Dawley rats (Hellier et al. [1998] Epilepsy Res. 31:73-84), a much lower cumulative dose of KA leads to robust chronic epilepsy in F344 rats. Furthermore, the occurrence of SRMS in this model is always associated with considerable bilateral hippocampal neurodegeneration and aberrant MFS. However, more extensive hippocampal CA3 cell loss and aberrant MFS do not appear to increase the frequency of SRMS. Because most of the features are consistent with mesial TLE in humans, the F344 model appears ideal for testing the efficacy of potential treatment strategies for mesial TLE.

Topics: Animals; Behavior, Animal; Cell Death; Disease Models, Animal; Electroencephalography; Epilepsy, Temporal Lobe; Fluoresceins; Forelimb; Functional Laterality; Hippocampus; Immunohistochemistry; In Situ Nick-End Labeling; Kainic Acid; Male; Mossy Fibers, Hippocampal; Neuropeptide Y; Organic Chemicals; Phosphopyruvate Hydratase; Rats; Rats, Inbred F344; Seizures; Silver Staining; Time Factors

Neuropeptide Y (NPY) has been shown to modulate seizure activities. To provide further understanding of the involvement of two of the most abundantly expressed NPY receptors, Y1 and Y2, we assessed the effect of Y1 and Y2 gene deletion on systemic kainic acid-induced seizures. We also examined the effect of rAAV-mediated hippocampal NPY overexpression on seizure susceptibility in these receptor knockout mice.. Recombinant adeno-associated viral vector overexpressing NPY (rAAV-NPY) or an empty vector control (rAAV-Empty) was injected into the hippocampus of adult C57BL/6-129/SvJ wild-type male mice and mice deficient of Y1 or Y2 receptors on the same background. Four weeks after vector injection, mice were subjected to systemic kainic acid-induced seizures, and the seizure behaviors were scored.. The rAAV-mediated hippocampal overexpression of NPY led to a twofold reduction in seizures induced by systemic kainic acid in wild-type mice and Y1 receptor knockout mice but not in mice deficient of Y2 receptors. A differential action by the receptors was observed in the seizure-induced mortality rate, with increased fatality in Y2-/- mice. In addition, although NPY overexpression did not significantly affect the mortality rate in Y2-/- and wild-type mice, it abolished KA-induced mortality in Y1-/-mice.. This study shows for the first time an altered susceptibility to chemically induced seizures in Y1 and Y2 knockout mice and demonstrates a differential seizure modulation mediated by these receptors via a genetic approach.

Topics: Animals; Dependovirus; DNA, Recombinant; Genetic Vectors; Hippocampus; Kainic Acid; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide Y; Receptors, Neuropeptide Y; Seizures

Although electroconvulsive seizures (ECS) are widely used as a treatment for severe depression, the working mechanism of ECS remains unclear. Repeated ECS causes anticonvulsant effects that have been proposed to underlie the therapeutic effect of ECS, and neuropeptide Y (NPY) is a potential candidate for mediating this anticonvulsant effect. Repeated ECS results in prominent increases in NPY synthesis. In contrast, NPY-sensitive receptor binding is decreased, so it is unclear whether ECS causes a net increase in NPY signalling. Agonist-stimulated [35S]GTPgammaS binding is a method for detecting functional activation of G-protein-coupled receptors. The present study in mice examined the effects of daily ECS for 14 days on NPY-stimulated [35S]GTPgammaS functional binding and compared this with gene expression of NPY and NPY receptors as well as [125I]peptide YY (PYY) binding in hippocampus of the same animals. Significant increases in NPY mRNA and concomitant reductions in NPY-sensitive binding were found in the dentate gyrus, hippocampal CA1, and neocortex of ECS treated mice, which is consistent with previous rat data. These changes remained significant 1 week after repeated ECS. Significant increases in NPY Y1, Y2, and Y5 mRNA were found in the dentate gyrus after ECS. Surprisingly, unaltered levels of functional NPY receptor binding accompanied the decreased NPY-sensitive binding. This suggests that mechanisms coupling NPY receptor stimulation to G-protein activation could be augmented after repeated ECS. Thus increased synthesis of NPY after repeated ECS should result in a net increase in NPY signalling in spite of reduced levels of NPY-sensitive binding.

Topics: Animals; Brain Chemistry; Electroshock; Female; Guanosine 5'-O-(3-Thiotriphosphate); Hippocampus; In Situ Hybridization; Mice; Mice, Inbred Strains; Neuropeptide Y; Receptors, Neuropeptide Y; RNA, Messenger; Seizures; Signal Transduction

Neuropeptide Y (NPY) potently inhibits glutamate release and seizure activity in rodent hippocampus in vitro and in vivo, but the nature of the receptor(s) mediating this action is controversial. In hippocampal slices from rats and several wild-type mice, a Y2-preferring agonist mimicked, and the Y2-specific antagonist BIIE0246 blocked, the NPY-mediated inhibition both of glutamatergic transmission and of epileptiform discharges in two different slice models of temporal lobe epilepsy, stimulus train-induced bursting (STIB) and 0-Mg2+ bursting. Whereas Y5 receptor-preferring agonists had small but significant effects in vitro, they were blocked by BIIE0246, and a Y5 receptor-specific antagonist did not affect responses to any agonist tested in any preparation. In slices from mice, NPY was without effect on evoked potentials or in either of the two slice seizure models. In vivo, intrahippocampal injections of Y2- or Y5-preferring agonists inhibited seizures caused by intrahippocampal kainate, but again the Y5 agonist effects were insensitive to a Y5 antagonist. Neither Y2- nor Y5-preferring agonists affected kainate seizures in mice. A Y5-specific antagonist did not displace the binding of two different NPY ligands in WT or mice, whereas all NPY binding was eliminated in the mouse. Thus, we show that Y2 receptors alone mediate all the anti-excitatory actions of NPY seen in the hippocampus, whereas our findings do not support a role for Y5 receptors either in vitro or in vivo. The results suggest that agonists targeting the Y2 receptor may be useful anticonvulsants.

Topics: Animals; Anticonvulsants; Arginine; Autoradiography; Benzazepines; Electric Stimulation; Electroencephalography; Electrophysiology; Excitatory Amino Acid Agonists; Hippocampus; In Vitro Techniques; Kainic Acid; Magnesium; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide Y; Rats; Receptors, Neuropeptide Y; Seizures; Synapses

Changed neuropeptide Y (NPY) system in the hippocampus has been reported in various experimental epileptic models. However, there have been little data concerning the alteration in the NPY system in the epileptic hippocampus following treatment of anti-epileptic drugs (AEDs). In the present study, therefore, we performed analyses of effects of vigabatrin (VGB) and zonisamide (ZNS) treatment on the NPY system in the hippocampus of the seizure sensitive (SS) gerbils. In SS gerbil, NPY immunoreactivity in the hippocampus was lower than that in seizure resistant gerbil. Following VGB treatment, the number of NPY immunoreactive neurons and NPY mRNA expression were increased in the hilus and the hippocampus proper. In contrast, ZNS treatment markedly elevated only the density of NPY immunoreactive fibers in the dentate gyrus, not in the hippocampus proper, as compared with saline-treated animals. These patterns were observed in the dose-dependent manners. These findings suggest that AEDs treatments may distinctly affect the NPY system in the SS gerbil hippocampus.

Topics: Animals; Anticonvulsants; Gerbillinae; Hippocampus; In Situ Hybridization; Isoxazoles; Neuropeptide Y; Seizures; Vigabatrin; Zonisamide

Despite numerous experiments showing that administration of neuropeptide Y (NPY) to rodents stimulates feeding and obesity, whereas acute interference with NPY signaling disrupts feeding and promotes weight loss, NPY-null mice have essentially normal body weight regulation. These conflicting observations suggest that chronic lack of NPY during development may lead to compensatory changes that normalize regulation of food intake and energy expenditure in the absence of NPY. To test this idea, we used gene targeting to introduce a doxycycline (Dox)-regulated cassette into the Npy locus, such that NPY would be expressed until the mice were given Dox, which blocks transcription. Compared with wild-type mice, adult mice bearing this construct expressed approximately 4-fold more Npy mRNA, which fell to approximately 20% of control values within 3 days after treatment with Dox. NPY protein also fell approximately 20-fold, but the half-life of approximately 5 days was surprisingly long. The biological effectiveness of these manipulations was demonstrated by showing that overexpression of NPY protected against kainate-induced seizures. Mice chronically overexpressing NPY had normal body weight, and administration of Dox to these mice did not suppress feeding. Furthermore, the refeeding response of these mice after a fast was normal. We conclude that, if there is compensation for changes in NPY levels, then it occurs within the time it takes for Dox treatment to deplete NPY levels. These observations suggest that pharmacological inhibition of NPY signaling is unlikely to have long-lasting effects on body weight.

Topics: Aging; Alleles; Animals; Appetite; Body Weight; Brain; Feeding Behavior; Gene Expression Regulation; Half-Life; Kainic Acid; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neuropeptide Y; RNA, Messenger; Seizures

Neuropeptide Y (NPY) inhibits seizures in experimental models and reduces excitability in human epileptic tissue. We studied the effect of long-lasting NPY overexpression in the rat hippocampus with local application of recombinant adeno-associated viral (AAV) vectors on acute kainate seizures and kindling epileptogenesis. Transgene expression was significantly increased by 7 d, reached maximal expression by 2 weeks, and persisted for at least 3 months. Serotype 2 AAV vector increased NPY expression in hilar interneurons, whereas the chimeric serotype 1/2 vector caused far more widespread expression, also including mossy fibers, pyramidal cells, and the subiculum. EEG seizures induced by intrahippocampal kainate were reduced by 50-75%, depending on the vector serotype, and seizure onset was markedly delayed. In rats injected with the chimeric serotype 1/2 vector, status epilepticus was abolished, and kindling acquisition was significantly delayed. Thus, targeted NPY gene transfer provides a potential therapeutic principle for the treatment of drug-resistant partial epilepsies.

Topics: Animals; Dependovirus; Disease Models, Animal; Electroencephalography; Epilepsy; Gene Expression; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Hippocampus; Injections, Intraventricular; Kainic Acid; Kindling, Neurologic; Male; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Seizures; Treatment Outcome

Neuropeptide Y (NPY) and galanin are neuropeptides that are regulated by energy states and are also anticonvulsant. We tested the hypothesis that the anticonvulsant efficacy of the ketogenic diet (KD) is mediated by increased expression of NPY and galanin via alterations in food intake and energy metabolism. In situ hybridization revealed no effect of the KD on NPY or galanin mRNA expression, suggesting that increased expression of NPY and galanin do not contribute to the anticonvulsant effect of the KD.

Topics: 3-Hydroxybutyric Acid; Animals; Brain Chemistry; Eating; Energy Metabolism; Epilepsy; Galanin; In Situ Hybridization; Ketones; Mice; Mice, Inbred C57BL; Neuropeptide Y; RNA, Messenger; Seizures

Organotypic hippocampal slice cultures were treated with the muscarinic agonist pilocarpine to study induced seizure-like activity and changes in neurotrophin and neuropeptide expression. For establishment of a seizure-inducing protocol, 2-week-old cultures derived from 6-8-day-old rats were exposed to 0.1 mM to 5 mM of pilocarpine for 4 h to 7 days. Other cultures were treated with pilocarpine for 7 days and left for 7-14 days in normal medium. Age-matched, non-treated cultures served as controls. Intracellular recordings from CA1 pyramidal cells revealed increased spontaneous activity in 31 of 35 cultures superfused with 0.1 or 5 mM pilocarpine. Epileptiform discharges were recorded in 17 of the 31 cultures, and 19 displayed frequencies specifically in the 6-12-Hz (Theta rhythm) range when superfused with pilocarpine. The pilocarpine effect was blocked by simultaneous superfusion with the muscarinic receptor antagonist atropine (100 microM). Regardless of dose and exposure time, the pilocarpine treatment induced very limited neuronal cell death, recorded as cellular propidium iodide uptake. Cultures exposed to 5 mM pilocarpine for up to 7 days displayed increased BDNF expression when analyzed by Western blot and ELISA. This BDNF increase correlated with increased neuropeptide Y immunoreactivity, known to accompany seizure activity. Addition of BDNF (200 ng/ml) to otherwise untreated cultures also upregulated NPY expression. The pilocarpine-induced seizure-like activity in hippocampal slice cultures, with concomitant increase in BDNF and NPY expression, is compared with in vivo observations and discussed in terms of the potential use of the easily accessible slice cultures in experimental seizure research.

Topics: Animals; Brain-Derived Neurotrophic Factor; Hippocampus; Humans; Neuropeptide Y; Organ Culture Techniques; Pilocarpine; Rats; Rats, Wistar; Seizures

Trimethyltin (TMT) is an organic metal known to induce neuronal degeneration in the hippocampus, and abnormal behavior characterized by seizures, increased aggression and memory deficits. We administered TMT to rats and studied the changes of neuropeptide Y (NPY) and somatostatin (SOM) in the hippocampus. Phenobarbital (PB) was administered as an anticonvulsant to assess the effect of seizures on neuropeptide expressions in both dorsal and ventral hippocampus. Histochemically, NPY-immunoreactivity increased 4 days after TMT treatment in the hilus of the hippocampus, then progressively decreased and dropped to a level below control 16 days after TMT treatment. Detection of NPY mRNA by in situ hybridization preceded the detection of NPY by immunohistochemistry. NPY mRNA signals increased in the hilus 2 days after TMT treatment. SOM-immunoreactivity also increased in the hilus of the hippocampus 2 days after TMT treatment, then decreased rapidly to a normal level. Similar changes in SOM mRNA were demonstrated by in situ hybridization. PB treatment significantly inhibited changes of NPY in terms of both immunoreactivity and mRNA expression; however, the same treatment failed to affect changes in SOM expression. This suggests that NPY and SOM act by different mechanisms in TMT-induced neurodegeneration.

Topics: Animals; Anticonvulsants; Benzoxazines; Cell Count; Coloring Agents; Hippocampus; Immunohistochemistry; In Situ Hybridization; Male; Neuropeptide Y; Oxazines; Phenobarbital; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures; Somatostatin; Trimethyltin Compounds

Neuropeptide Y (NPY) has been proposed to play a role in the pathophysiology of depression and also to act as an endogenous anticonvulsant. Repeated administration of electroconvulsive stimulations (ECS) has been shown to induce a long-term increase in hippocampal NPY neurotransmission, while the effects of single ECS are largely unexplored. In this study, we assessed extracellular levels of NPY in the dorsal hippocampus of freely moving rats following a single ECS. We also studied the effect of locally administered BIBP3226, a selective NPY Y1 receptor antagonist with reported anticonvulsant properties, on the duration of the ECS-induced seizure and NPY release in freely moving animals. Our data demonstrate that a single ECS increases extracellular NPY-like immunoreactivity (LI) levels in the dorsal hippocampus, reaching statistical significance 2h following the treatment. KCl transiently and calcium-dependently increased extracellular levels of NPY, suggesting that the measured NPY-LI is derived from functional neurons. Local BIBP3226 perfusion essentially abolished the ECS-induced seizure but had no effect on the basal NPY-LI outflow or on the ECS-induced rise in extracellular NPY levels. Our data are in line with the hypothesis that one mechanism of action of ECS is to release NPY in the hippocampus and suggest that the increase is in itself not associated with anticonvulsant activity but may represent other properties of NPY.

Topics: Animals; Anticonvulsants; Arginine; Calcium; Electroshock; Extracellular Space; Hippocampus; Male; Microdialysis; Neuropeptide Y; Potassium Chloride; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Receptors, Neuropeptide Y; Seizures

The rat dentate gyrus is usually described as relatively homogeneous. Here, we present anatomic and physiological data which demonstrate that there are striking differences between the supra- and infrapyramidal blades after status epilepticus and recurrent seizures. These differences appear to be an accentuation of a subtle asymmetry present in normal rats. In both pilocarpine and kainic acid models, there was greater mossy fiber sprouting in the infrapyramidal blade. This occurred primarily in the middle third of the hippocampus. Asymmetric sprouting was evident both with Timm stain as well as antisera to brain-derived neurotrophic factor (BDNF) or neuropeptide Y (NPY). In addition, surviving NPY-immunoreactive hilar neurons were distributed preferentially in the suprapyramidal region of the hilus. Extracellular recordings from infrapyramidal sites in hippocampal slices of pilocarpine-treated rats showed larger population spikes and weaker paired-pulse inhibition in response to perforant path stimulation relative to suprapyramidal recordings. A single stimulus could evoke burst discharges in infrapyramidal granule cells but not suprapyramidal blade neurons. BDNF exposure led to spontaneous epileptiform discharges that were larger in amplitude and longer lasting in the infrapyramidal blade. Stimulation of the infrapyramidal molecular layer evoked larger responses in area CA3 than suprapyramidal stimulation. In slices from the temporal pole, in which anatomic evidence of asymmetry waned, there was little evidence of physiological asymmetry either. Of interest, some normal rats also showed signs of greater evoked responses in the infrapyramidal blade, and this could be detected with both microelectrode recording and optical imaging techniques. Although there were no signs of hyperexcitability in normal rats, the data suggest that there is some asymmetry in the normal dentate gyrus and this asymmetry is enhanced by seizures. Taken together, the results suggest that supra- and infrapyramidal blades of the dentate gyrus could have different circuit functions and that the infrapyramidal blade may play a greater role in activating the hippocampus.

Topics: Animals; Brain-Derived Neurotrophic Factor; Dentate Gyrus; Electrophysiology; Excitatory Amino Acid Agonists; Immunohistochemistry; Kainic Acid; Male; Mossy Fibers, Hippocampal; Muscarinic Agonists; Neuropeptide Y; Pilocarpine; Rats; Rats, Sprague-Dawley; Seizures; Status Epilepticus; Synapses

The results of several studies have contributed to the hypothesis that BDNF promotes seizure activity, particularly in adult hippocampus. To test this hypothesis, BDNF, vehicle (phosphate-buffered saline, PBS), or albumin was infused directly into the hippocampus for 2 weeks using osmotic minipumps. Rats were examined behaviorally, electrophysiologically, and anatomically. An additional group was tested for sensitivity to the convulsant pilocarpine. Spontaneous behavioral seizures were observed in BDNF-infused rats (8/32; 25%) but not in controls (0/20; 0%). In a subset of six animals (three BDNF, three albumin), blind electrophysiological analysis of scalp recordings contralateral to the infused hippocampus demonstrated abnormalities in all BDNF rats; but not controls. Neuronal loss in BDNF-treated rats was not detected relative to PBS- or albumin-treated animals, but immunocytochemical markers showed a pattern of expression in BDNF-treated rats that was similar to rats with experimentally induced seizures. Thus, BDNF-infused rats had increased expression of NPY in hilar neurons of the dentate gyrus relative to control rats. NPY and BDNF expression was increased in the mossy fiber axons of dentate gyrus granule cells relative to controls. The increase in NPY and BDNF expression in BDNF-treated rats was bilateral and occurred throughout the septotemporal axis of the hippocampus. Mossy fiber sprouting occurred in five BDNF-treated rats but no controls. In another group of infused rats that was tested for seizure sensitivity to the convulsant pilocarpine, BDNF-infused rats had a shorter latency to status epilepticus than PBS-infused rats. In addition, the progression from normal behavior to severe seizures was faster in BDNF-treated rats. These data support the hypothesis that intrahippocampal BDNF infusion can facilitate, and potentially initiate, seizure activity in adult hippocampus.

Topics: Animals; Behavior, Animal; Brain-Derived Neurotrophic Factor; Dentate Gyrus; Disease Models, Animal; Disease Progression; Dose-Response Relationship, Drug; Drug Administration Routes; Electroencephalography; Hippocampus; Infusions, Parenteral; Limbic System; Male; Mossy Fibers, Hippocampal; Neuropeptide Y; Pilocarpine; Rats; Seizures; Status Epilepticus

Although it is now established that neurogenesis of dentate gyrus granule cells increases after experimental seizures, little is currently known about the function of the new granule cells. One question is whether they become integrated into the network around them. Recent experiments that focused on the newly born granule cells in the hilus showed that indeed the new cells appear to become synchronized with host hippocampal neurons [Scharfman et al. (2000) J. Neurosci. 20, 6144-6158]. To address this issue further, we asked whether the new hilar granule cells were active during spontaneous limbic seizures that follow status epilepticus induced by pilocarpine injection. Thus, we perfused rats after spontaneous seizures and stained sections using antibodies to c-fos, a marker of neural activity, and calbindin, a marker of the newly born hilar granule cells [Scharfman et al. (2000) J. Neurosci. 20, 6144-6158]. We asked whether calbindin-immunoreactive hilar neurons were also c-fos-immunoreactive.C-fos was highly expressed in calbindin-immunoreactive hilar neurons. Approximately 23% of hilar cells that expressed c-fos were double-labeled for calbindin. In addition, other types of hilar neurons, i.e. those expressing parvalbumin or neuropeptide Y, also expressed c-fos. Yet other hippocampal neurons, including granule cells and pyramidal cells, had weak expression of c-fos at the latency after the seizure that hilar neuron expression occurred. In controls, there was very little c-fos or calbindin expression in the hilus.These results indicate that calbindin-immunoreactive hilar cells are activated by spontaneous seizures. Based on the evidence that many of these cells are likely to be newly born, the data indicate that new cells can become functionally integrated into limbic circuits involved in recurrent seizure generation. Furthermore, they appear to do so in a manner similar to many neighboring hilar neurons, apparently assimilating into the local environment. Finally, the results show that a number of hilar cell types are activated during chronic recurrent seizures in the pilocarpine model, a surprising result given that many hilar neurons are thought to be damaged soon after pilocarpine-induced status epilepticus.

Topics: Animals; Calbindins; Cell Count; Dentate Gyrus; Male; Neurons; Neuropeptide Y; Parvalbumins; Pilocarpine; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Recurrence; S100 Calcium Binding Protein G; Seizures; Status Epilepticus

Changes in neuropeptide Y (NPY) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d)-positive neurons in the hippocampus were investigated 5, 10 and 20 days after kainic acid (KA) administration using a double labeling method. The numbers of NADPH-d-positive-only and NPY/NADPH-d-positive neurons decreased in the CA1/2-CA3 regions of the hippocampus, 5, 10 and 20 days after KA administration, however, the number of NPY-positive-only neurons increased in the same regions 5 and 10 days after KA administration. In the dentate gyrus (DG) region of the hippocampus, the numbers of NPY-positive-only, NADPH-d-positive-only and NPY/NADPH-d-positive neurons increased 5 days after KA administration, and 20 days after KA administration, the number of NADPH-d-positive-only neurons decreased to levels similar to or lower than the level of the controls. However, the numbers of NPY/NADPH-d-positive and NPY-positive-only neurons in the DG region 20 days after KA administration remained at control levels. These results indicate that, NADPH-d-positive-only neurons are vulnerable to, and NPY-positive-only neurons are resistant to KA-induced seizures in the whole hippocampus, but that NPY/NADPH-d-positive neurons have different sensitivities in subregions of the hippocampus to KA-induced seizures. In addition, the present findings provide the first statistical and morphological evidence, which demonstrates that NPY-positive-only, NADPH-d-positive-only and NPY/NADPH-d-positive neurons in the hippocampus have different sensitivities to KA-induced seizures.

Topics: Animals; Excitatory Amino Acid Agonists; Hippocampus; Immunoenzyme Techniques; Kainic Acid; Male; NADPH Dehydrogenase; Neurons; Neuropeptide Y; Rats; Rats, Inbred F344; Seizures

Intracerebroventricular injection of NPY inhibits epileptiform seizures and seizure-related "wet dog shakes" (WDS) following electrical stimulation of the dentate gyrus or subiculum. This study examined the effects of NPY on seizures and WDS elicited in hippocampal CA3. Like in the other hippocampal regions, NPY significantly inhibited both seizures and accompanying WDS consistent with in vitro data. The identification of an additional antiepileptic hippocampal target for NPY could prove therapeutically relevant considering that the hippocampal formation is a frequent seizure focus in human epilepsy. The effects of NPY were found to persist on seven repeated NPY injection days. Thus tolerance to the anti-seizure effects of NPY does not appear to develop rapidly. Tolerance being a problem with several current antiepileptic drugs, this further strengthens the concept of NPY receptors as a potential future antiepileptic target.

Topics: Animals; Anticonvulsants; Dentate Gyrus; Epilepsy; Hippocampus; Male; Neuropeptide Y; Rats; Rats, Wistar; Seizures; Time Factors

In vitro and in vivo experiments suggest antiepileptic properties for NPY. In this study, the pharmacology of these effects was examined and compared in different rat models of seizures. Agonists for Y(1), Y(2) and Y(5) receptors reduced seizure-like activity in hippocampal cultures. Intracerebral injection of NPY or Y(5) agonists reduced the expression of focal seizures produced by a single electrical stimulation of the hippocampus. Conversely, NPY agonists increased the duration of generalized convulsive seizures induced by pentylenetetrazol. These results suggest that NPY reduces seizures of hippocampal origin through activation of Y(5) receptors. They also point to probable modulatory effects of NPY in brain structures other than the hippocampus, involved in initiation, propagation or control of seizures.

Topics: Animals; Anticonvulsants; Cells, Cultured; Epilepsy; Hippocampus; Male; Neuropeptide Y; Pentylenetetrazole; Rats; Rats, Wistar; Receptors, Neuropeptide Y; Seizures; Time Factors

The clinical and basic literature suggest that hilar cells of the dentate gyrus are damaged after seizures, particularly prolonged and repetitive seizures. Of the cell types within the hilus, it appears that the mossy cell is one of the most vulnerable. Nevertheless, hilar neurons which resemble mossy cells appear in some published reports of animal models of epilepsy, and in some cases of human temporal lobe epilepsy. Therefore, mossy cells may not always be killed after severe, repeated seizures. However, mossy cell survival in these studies was not completely clear because the methods did allow discrimination between mossy cells and other hilar cell types. Furthermore, whether surviving mossy cells might have altered physiology after seizures was not examined. Therefore, intracellular recording and intracellular dye injection were used to characterize hilar cells in hippocampal slices from pilocarpine-treated rats that had status epilepticus and recurrent seizures ('epileptic' rats). For comparison, mossy cells were also recorded from age-matched, saline-injected controls, and pilocarpine-treated rats that failed to develop status epilepticus. Numerous hilar cells with the morphology, axon projection, and membrane properties of mossy cells were recorded in all three experimental groups. Thus, mossy cells can survive severe seizures, and those that survive retain many of their normal characteristics. However, mossy cells from epileptic tissue were distinct from mossy cells of control rats in that they generated spontaneous and evoked epileptiform burst discharges. Area CA3 pyramidal cells also exhibited spontaneous and evoked bursts. Simultaneous intracellular recordings from mossy cells and pyramidal cells demonstrated that their burst discharges were synchronized, with pyramidal cell discharges typically beginning first. From these data we suggest that hilar mossy cells can survive status epilepticus and chronic seizures. The fact that mossy cells have epileptiform bursts, and that they are synchronized with area CA3, suggest a previously unappreciated substrate for hyperexcitability in this animal model.

Topics: Action Potentials; Animals; Biotin; Cell Size; Cell Survival; Cortical Synchronization; Dendrites; Epilepsy, Temporal Lobe; Immunohistochemistry; Interneurons; Male; Mossy Fibers, Hippocampal; Muscarinic Agonists; Neural Pathways; Neuronal Plasticity; Neuropeptide Y; Pilocarpine; Pyramidal Cells; Rats; Rats, Sprague-Dawley; Seizures; Status Epilepticus; Synaptic Transmission

Epilepsy is a disease of neuronal hyperexcitability, and pharmacological and genetic studies have identified norepinephrine (NE) and neuropeptide Y (NPY) as important endogenous regulators of neuronal excitability. Both transmitters signal through G-protein-coupled receptors, are expressed either together or separately, and are abundant in brain regions implicated in seizure generation. NPY knock-out (NPY KO) and dopamine beta-hydroxylase knock-out (DBH KO) mice that lack NE are susceptible to seizures, and agonists of NE and NPY receptors protect against seizures. To examine the relative contributions of NE and NPY to neuronal excitability, we tested Dbh;Npy double knock-out (DKO) mice for seizure sensitivity. In general, DBH KO mice were much more seizure-sensitive than NPY KO mice and had normal NPY expression, demonstrating that an NPY deficiency did not contribute to the DBH KO seizure phenotype. DKO mice were only slightly more sensitive than DBH KO mice to seizures induced by kainic acid, pentylenetetrazole, or flurothyl, although DKO mice were uniquely prone to handling-induced seizures. NPY contributed to the seizure phenotype of DKO mice at high doses of convulsant agents and advanced stages of seizures. These data suggest that NE is a more potent endogenous anticonvulsant than NPY, and that NPY has the greatest contribution under conditions of extreme neuronal excitability.

Topics: Animals; Dopamine beta-Hydroxylase; Exercise Test; Flurothyl; Genetic Predisposition to Disease; Handling, Psychological; In Situ Hybridization; Kainic Acid; Male; Mice; Mice, Knockout; Neuropeptide Y; Norepinephrine; Pentylenetetrazole; Phenotype; Seizures

Stimulation of glutamate receptors has been reported to modulate the expression of neuropeptides and their receptors in neurons. On the other hand, neuropeptides are known to regulate the presynaptic glutamate release and neuronal responses to excitatory neurotransmission. This evidence indicates a functional interaction between glutamatergic and neuropeptidergic transmission in the central nervous system (CNS). In this report, we provide pharmacologic evidence in experimental models of seizures, suggesting that somatostatin (SRIF) and neuropeptide Y (NPY) are endogenous modulators of glutamate-mediated hyperexcitability in the CNS. Electroencephalographic (EEG) and behavioral seizures were induced in rats by intrahippocampal or systemic injection of kainic acid, a glutamate analog. The number of EEG seizures and their total duration were inhibited significantly by intracerebral application of a SRIF(1) receptor agonist. Similarly, kainate seizures were reduced by N[-2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl-D-arginamide++ +] (BIBP 3226), a NPY Y(1) receptor antagonist. Enhanced seizure susceptibility to pentylentetrazol, ensuing in rats after a systemic administration of kainic acid, was reduced significantly by intracerebral application of RC 160, a SRIF(1) receptor agonist, or NPY 13-36, a Y(2)/Y(5) receptor agonist. This evidence suggests that neuropeptide analogs may be of value for controlling seizures and possibly in other pathologic conditions associated with excessive glutamate function.

Topics: Animals; Anticonvulsants; Arginine; Convulsants; Kainic Acid; Male; Neuropeptide Y; Neuropeptides; Octreotide; Pentylenetetrazole; Peptide Fragments; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Receptors, Neuropeptide Y; Receptors, Somatostatin; Seizures; Somatostatin

The functional role of the calcium-binding proteins parvalbumin, calretinin, and calbindin D-28k for epileptogenesis and long-term seizure-related alterations of the hippocampal formation was assessed in single- and double-knockout mice, using a kainate model of mesial temporal lobe epilepsy. The effects of a unilateral intrahippocampal injection of kainic acid were assessed at one day, 30 days, and four months post-injection, using various markers of GABAergic interneurons (GABA-transporter type 1, GABA(A)-receptor alpha1 subunit, calretinin, calbindin D-28k, somatostatin, and neuropeptide Y). Parvalbumin-deficient, parvalbumin/calbindin-deficient, and parvalbumin/calretinin-deficient mice exhibited no difference in cytoarchitecture of the hippocampal formation and in the number, distribution, or morphology of interneurons compared to wild-type mice. Likewise, mutant mice were not more vulnerable to acute kainate-induced excitotoxicity or to long-term effects of recurrent focal seizures, and exhibited the same pattern of neurochemical alterations (e.g., bilateral induction of neuropeptide Y in granule cells) and morphogenic changes (enlargement and dispersion of dentate gyrus granule cells) as wild-type animals. Quantification of interneurons revealed no significant difference in neuronal vulnerability among the genotypes.These results indicate that the calcium-binding proteins investigated here are not essential for determining the neurochemical phenotype of interneurons. Furthermore, they are not protective against kainate-induced excitotoxicity in this model, and do not appear to modulate the overall level of excitability of the hippocampus. Finally, seizure-induced changes in gene expression in granule cells, which normally express high levels of calcium-binding proteins, apparently were not affected by the gene deletions analysed.

Topics: Animals; Calbindin 2; Calbindins; Calcium-Binding Proteins; Carrier Proteins; Cell Survival; Disease Models, Animal; Epilepsy, Temporal Lobe; Excitatory Amino Acid Agonists; GABA Plasma Membrane Transport Proteins; Gene Expression Regulation; Hippocampus; Immunohistochemistry; Interneurons; Kainic Acid; Membrane Proteins; Membrane Transport Proteins; Mice; Mice, Knockout; Neurodegenerative Diseases; Neuropeptide Y; Organic Anion Transporters; Parvalbumins; Receptors, GABA-A; S100 Calcium Binding Protein G; Seizures; Somatostatin

Previous experiments have reported increased seizure susceptibility in transgenic mice lacking normal neuropeptide-Y (NPY) gene expression (i.e. NPY 'knock-out' mice). A critical issue inherent in such experiments concerns the confounding of developmental influences of NPY and its neurotransmitter functions in the mature organism. The present experiments directly addressed this issue by studying seizure susceptibility in transgenic mice possessing an inducible antisense transcript that can be experimentally manipulated to attenuate NPY synthesis. NPY-deficient and control mice were injected with kainic acid (40 mg/kg, i.p.) and several seizure-related behaviors were measured. Consistent with previously reported effects in NPY knock-out mice, significantly more NPY-deficient mice died within 24 h than control mice. In situ hybridization analyses confirmed a decrease in prepro-NPY gene expression in transgenic mice. The experiments support the hypothesis that the control of neural excitability is a prominent function of NPY.

Topics: Animals; Female; Gene Expression Regulation; Hippocampus; Kainic Acid; Male; Mice; Mice, Transgenic; Neurons; Neuropeptide Y; RNA, Messenger; Seizures

Repeated electroconvulsive stimulations and other seizure modalities produce an increase in neuropeptide Y synthesis and local release in the rat hippocampus, and perhaps as a consequence, a change in the concentration of neuropeptide Y binding sites in the same region. The aim of the present study was to determine possible changes in the expression of neuropeptide Y receptor subtypes affected by repeated stimulations in the hippocampus. Rats were exposed to 14 daily stimulations, and the brains were removed 24h after the last stimulation. For in vitro receptor autoradiography and in situ hybridisation histochemistry, the brains were frozen, sectioned, and levels of neuropeptide Y binding sites and messenger RNA expressions were determined quantitatively on sections from the same animals. In order to determine the contribution of different neuropeptide Y receptor subtypes, serial sections were incubated with either 125I-labelled peptide YY alone or the same radio-labelled peptide mixed with an excess of a number of displacing compounds with affinity for either neuropeptide Y receptor subtype Y1, Y2, or both. Binding studies revealed that the majority of peptide YY binding sites was represented by Y2, and that electroconvulsive stimulations reduced the binding capacity or the concentration of this receptor. A prominent reduction of Y1-preferring binding sites was determined in the dentate gyrus, and to a lesser extent in the CA1 and CA3 regions. Similarly, the treatment produced a significant reduction of Y2-preferring binding sites in the CA1 and CA3 region, but not in the granular cell layer of the dentate gyrus. Using semi-quantitative in situ hybridization, Y1 receptor messenger RNA level in the granular cell layer of the dentate increased by the stimulations. In the same region, Y2 receptor messenger RNA was expressed in low to undetectable amounts, but after the repeated stimulations, this transcript was found in moderate to high levels. These data suggest that the neuropeptide Yergic system in the dentate gyrus and the pyramidal cell layer are affected by the treatment, and that this includes both Y1 and Y2 receptor subtypes. Because levels of messenger RNA and binding are distinctly regulated, the turnover of both Y1 and Y2 molecules is strongly increased under electroconvulsive stimulations, suggesting that the intrahippocampal neuropeptide Yergic neurotransmission is also increased under the stimulations.

Topics: Animals; Anti-Anxiety Agents; Arginine; Autoradiography; Down-Regulation; Electric Stimulation Therapy; Epilepsy; Gene Expression; Hippocampus; In Situ Hybridization; Iodine Radioisotopes; Male; Neuropeptide Y; Radioligand Assay; Rats; Rats, Wistar; Receptors, Neuropeptide Y; RNA, Messenger; Seizures

Recent studies reported changes in neuropeptide Y (NPY) expression induced by seizures in the experimental epileptic models. However, there have been few reports of the alteration of NPY expression in hippocampal complexes of genetic epilepsy models. In the present study, we performed spatial and temporal analyses of NPY expression in the hippocampal complexes of the seizure-resistant (SR) and seizure-sensitive (SS) gerbils, one of the genetic models. In SR gerbils, most NPY(+) cells were located at the dentate hilus (DH) and the subiculum (SC). In the pre-seizure group of SS gerbils, neurons in the DH and SC were nearly devoid of NPY immunoreactivity. Interestingly, the acute NPY expressions were observed in these areas of the post-seizure group at 30 min, and its immunoreactivity was declined at 12 h after the onset of seizure. These findings suggest that in seizure, the deficiency of NPY in DH and SC may be one of the factors, and that the acute expression of NPY after seizure in these areas may be the compensatory response for reduction of seizure activity in this animal.

Topics: Animals; Dentate Gyrus; Entorhinal Cortex; Epilepsy; Gerbillinae; Hippocampus; Immunohistochemistry; Neuropeptide Y; Seizures

Seizure threshold increases during a series of electroconvulsive therapy (ECTs). Based on assumptions that the effect of ECT may be related to its anticonvulsant effect we were interested in identifying transmitters that are activated by the treatment and play an anticonvulsant role. Animal studies reveal that neuropeptide Y (NPY) neurotransmission is increased by repeated electroconvulsive shock (ECS), and NPY has been found to inhibit glutamate-mediated synaptic transmission in the rat hippocampus. The increase of NPY gene expression in highly sensitive areas of the rat hippocampus (dentate gyrus) and piriform cortex accompanied by a reduction of NPY binding sites in the same regions after ECS supports this notion. Further studies have shown that NPY exerts a seizure-suppressing activity of NPY after kainic acid injections in vivo. Taken together the present series of experiments in rats strongly points to the seizure suppressing properties of NPY and suggests that this peptide may be involved in the seizure threshold increase during effective ECT in humans.

Topics: Animals; Cerebral Cortex; Electroconvulsive Therapy; Hippocampus; Male; Neural Conduction; Neuropeptide Y; Rats; Rats, Wistar; Receptors, Glutamate; Seizures; Synaptic Transmission

This study examined the acute actions of brain-derived neurotrophic factor (BDNF) in the rat dentate gyrus after seizures, because previous studies have shown that BDNF has acute effects on dentate granule cell synaptic transmission, and other studies have demonstrated that BDNF expression increases in granule cells after seizures. Pilocarpine-treated rats were studied because they not only have seizures and increased BDNF expression in granule cells, but they also have reorganization of granule cell "mossy fiber" axons. This reorganization, referred to as "sprouting," involves collaterals that grow into novel areas, i.e., the inner molecular layer, where granule cell and interneuron dendrites are located. Thus, this animal model allowed us to address the effects of BDNF in the dentate gyrus after seizures, as well as the actions of BDNF on mossy fiber transmission after reorganization. In slices with sprouting, BDNF bath application enhanced responses recorded in the inner molecular layer to mossy fiber stimulation. Spontaneous bursts of granule cells occurred, and these were apparently generated at the site of the sprouted axon plexus. These effects were not accompanied by major changes in perforant path-evoked responses or paired-pulse inhibition, occurred only after prolonged (30-60 min) exposure to BDNF, and were blocked by K252a. The results suggest a preferential action of BDNF at mossy fiber synapses, even after substantial changes in the dentate gyrus network. Moreover, the results suggest that activation of trkB receptors could contribute to the hyperexcitability observed in animals with sprouting. Because human granule cells also express increased BDNF mRNA after seizures, and sprouting can occur in temporal lobe epileptics, the results may have implications for understanding temporal lobe epilepsy.

Topics: Action Potentials; Animals; Brain-Derived Neurotrophic Factor; Cell Size; Epilepsy; Excitatory Postsynaptic Potentials; GABA Antagonists; In Vitro Techniques; Male; Mossy Fibers, Hippocampal; Neuropeptide Y; Pilocarpine; Rats; Rats, Sprague-Dawley; Receptor Protein-Tyrosine Kinases; Receptor, Ciliary Neurotrophic Factor; Receptors, GABA; Receptors, N-Methyl-D-Aspartate; Receptors, Nerve Growth Factor; Seizures; Status Epilepticus; Synapses; Synaptic Transmission

Kainic acid induces seizures and a rapid induction of immediate early genes and neuronal death. Neuropeptide Y (NPY) is implicated in seizure inhibiting activity. In order to investigate the mechanisms by which NPY inhibits seizure activity, this study was carried out to measure the levels of mRNAs encoding three different immediate early genes, in regions of the hippocampus and relate their induction to the behaviour in the same animals. NPY inhibited both the time spent in seizures, and the number of generalized seizures. However, NPY did not inhibit the induction of c-fos, FosB or junB mRNA in any hippocampal region examined in the same animals, showing lack of correlation between immediate early gene induction and seizure activity.

Topics: Animals; Dentate Gyrus; Gene Expression Regulation; Genes, fos; Genes, Immediate-Early; Genes, jun; Hippocampus; Kainic Acid; Male; Neuropeptide Y; Rats; Rats, Wistar; RNA, Messenger; Seizures; Transcription, Genetic; Transcriptional Activation

In this microdialysis study we measured the extracellular neuropeptide Y (NPY) levels in the dorsal hippocampus of conscious rats. During potassium-induced depolarisations, a 93% increase in extracellular levels of NPY was observed. NPY has been demonstrated to reduce kainic acid-induced convulsions in rats, but it is unknown whether NPY neurotransmission is affected by seizures. During seizures induced by kainic acid we observed a 104% increase in levels of NPY, suggesting that convulsions are associated with a dramatically increased NPYergic neurotransmission.

Topics: Animals; Hippocampus; Kainic Acid; Male; Microdialysis; Movement; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Seizures

Neuropeptide Y (NPY) gene expression is known to be modulated in the mossy fiber projection of hippocampal granule cells following seizure. We investigated NPY biosynthesis and metabolism in an attempt to characterize NPY biochemically as a neurotransmitter in the granule cell mossy fiber projection. NPY biosynthesis was compared in normal control animals and in animals that had experienced a single pentylenetetrazole-induced seizure. In situ hybridization analysis established the postseizure time course of preproNPY mRNA expression in the hippocampal formation, localizing the majority of increased preproNPY mRNA content to the hilus of the dentate gyrus. Radioimmunoassay analysis of the CA3/mossy fiber terminal subfield confirmed a subsequent increase in NPY peptide content. Biosynthesis of NPY peptide by granule cells and transport to the CA3/mossy fiber subfield was demonstrated by in vivo radiolabel infusion to the dentate gyrus/hilus followed by sequential HPLC purification of identified radiolabeled peptide from the CA3/mossy fiber terminal subfield. Additional in vivo radiolabeling studies revealed a postseizure increase in an unidentified NPY-like immunoreactive (NPY-LI) species. HPLC/radioimmunoassay analyses of CA3 subfield tissue extracts comparing normal control animals and pentylenetetrazole-treated animals confirmed the increased total NPY-LI, and demonstrated that the increased NPY-LI was comprised of a minor increase in native NPY and a major increase in the unknown NPY-LI. Data from subsequent and separate analyses incorporating immunoprecipitation with anti-C-terminal flanking peptide of NPY, further HPLC purification, and matrix-assisted laser desorption/ionization mass spectrometry support the conclusion that the unknown NPY-LI is methionine sulfoxide NPY. NPY and NPY-sulfoxide displayed differential calcium sensitivity for release from mossy fiber synaptosomes. Similar to NPY, NPY sulfoxide displayed high-affinity binding to each of the cloned Y1, Y2, Y4, and Y5 receptor subtypes. Postrelease inactivation of NPY was demonstrated in a mossy fiber synaptosomal preparation. Thus, the present study in combination with previously reported electrophysiological activity of NPY in the CA3 subfield demonstrates that NPY fulfills the classical criteria for a neurotransmitter in the hippocampal granule cell mossy fiber projection, and reveals the presence of two molecular forms of NPY that display differential mechanisms of release while maintai

Topics: Amino Acid Sequence; Animals; Binding, Competitive; Biological Transport; Hippocampus; Immunologic Techniques; Male; Methionine; Molecular Sequence Data; Mossy Fibers, Hippocampal; Nerve Endings; Neurons; Neuropeptide Y; Neuropeptides; Oxidation-Reduction; Pentylenetetrazole; Protein Precursors; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures; Synaptosomes

Intracerebroventricular (i.c.v.) administration of NPY inhibits limbic seizure activity induced by kainic acid or electrical hippocampal stimulation in vivo. Similarly, antiepileptiform effects have been demonstrated in hippocampal slice models. This suggests a possible antiepileptic potential of NPYergic agonists in future treatment of complex partial seizures in humans. To further characterize the antiepileptic potential of NPY, the effects of NPY administered i.c.v. were studied on seizures induced by subcutaneous injection of pentylenetetrazole (PTZ), a widely used antiepileptic screening test believed to model generalized myoclonic seizures. NPY significantly and dose-dependently inhibited PTZ-induced clonic seizures as revealed by increases in seizure latencies. In addition, NPY caused an overall significant reduction in the number of rats developing tonic seizures and in mortality following PTZ, indicating that NPY also reduces seizure severity. By demonstrating antiepileptic activity of NPY in yet another seizure model, this study further adds to the concept of NPY receptors as potentially novel targets in future treatment of seizure disorders. Specifically, antiepileptic effects in the PTZ model suggest that NPYergic agonists might also prove active against human myoclonic seizures.

Topics: Animals; Anticonvulsants; Convulsants; Disease Models, Animal; Humans; Injections, Intraventricular; Male; Neuropeptide Y; Pentylenetetrazole; Rats; Rats, Wistar; Receptors, Neuropeptide Y; Seizures

Kindling, a model of temporal lobe epilepsy, induces a number of neuropeptides including corticotropin-releasing factor (CRF). CRF itself can produce limbic seizures which resemble kindling in some aspects. However, tolerance to the convulsant effects of CRF develops rapidly. Hypothetically, this could be explained should seizures also induce the CRF-binding protein (CRF-BP), which has been postulated to restrict the actions of CRF. Therefore, in the present study, we used in situ hybridization to examine the effects of amygdala-kindled seizures on the mRNA levels of CRF and CRF-BP. Kindled seizures markedly elevated CRF and CRF-BP in the dentate gyrus of rats. CRF and CRF-BP were induced almost exclusively in GABAergic interneurons of the dentate hilus. The CRF and CRF-BP interneurons also expressed neuropeptide Y but not cholecystokinin. CRF appeared to have an excitatory role in the dentate gyrus as it decreased the afterhyperpolarization of dentate granule neurons. These results suggest that CRF may contribute to the development of amygdala kindling. However, the compensatory induction of CRF-BP may serve to limit the excitatory effects of CRF in the dentate gyrus.

Topics: Amygdala; Animals; Carrier Proteins; Cholecystokinin; Corticotropin-Releasing Hormone; Electrophysiology; gamma-Aminobutyric Acid; Hippocampus; In Situ Hybridization; In Vitro Techniques; Interneurons; Kindling, Neurologic; Male; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Seizures; Sheep

Neuropeptide Y (NPY) is widely distributed in interneurons of the central nervous system (CNS), including the hippocampus and cerebral cortex, in concentrations exceeding those of any other known neuropeptides. Sequence data comparing different species show that NPY is highly conserved. This suggests a critical role in regulation of regional neuronal excitability. Kainic acid, a glutamate agonist at kainic acid receptors, causes severe limbic motor seizures culminating in status epilepticus. We here report that NPY administered into the lateral ventricle is a powerful inhibitor of motor as well as electroencephalographic (EEG) seizures induced by kainic acid. This effect was mediated via receptors with a pharmacological profile similar to the recently cloned rat Y5 receptor. The present study is the first to demonstrate that NPY possesses anticonvulsant activity. This is consistent with the concept that NPY is an endogenous anticonvulsant and suggests that agonists acting at Y5-like receptors may constitute a novel group of drugs in antiepileptic therapy.

Topics: Animals; Anticonvulsants; Disease Models, Animal; Humans; Kainic Acid; Male; Neuropeptide Y; Proto-Oncogene Proteins c-fos; Rats; Rats, Wistar; Receptors, Neuropeptide Y; Seizures

Results from animal studies and from human tissue removed from epileptics show that certain subgroups of hippocampal neurons are more vulnerable to seizure activity than others. It is possible that neurons which contain calcium-binding proteins, such as parvalbumin, may be protected from the high calcium overload that results from seizure activity. In the present study, seizures were induced by an injection of tetanus toxin into the rat hippocampus. A morphological and quantitative analysis was made of the parvalbumin-containing neurons and of those which co-localized somatostatin and neuropeptide Y. At 2 weeks there was a generalized increase in immunoreactivity in both groups of neurons. From 1 month through to 3 months after injection, the up-regulation in immunoreactivity was sustained in the surviving hilar neurons which co-localized somatostatin and neuropeptide Y but there was a marked reduction in immunoreactivity of the parvalbumin neurons. Although there was no evidence for a loss of parvalbumin neurons there was a small and significant reduction in the number of somatostatin + neuropeptide Y double-labelled neurons in the contralateral hilus at 3 and 4 months after a tetanus injection. The vulnerability of the somatostatin + neuropeptide Y double-labelled hilar neurons but not of the parvalbumin-containing, presumed, basket cells are considered in terms of their connectivity.

Topics: Animals; Behavior, Animal; Cell Count; Dentate Gyrus; Hippocampus; Male; Neurons; Neuropeptide Y; Neuropeptides; Parvalbumins; Rats; Rats, Wistar; Seizures; Somatostatin; Tetanus Toxin

The effects of trimethyltin on the hippocampus were investigated in terms of changes in histology, depth electroencephalography, learning acquisition and memory retention, choline acetyltransferase and neuropeptides, and seizure-induced c-fos messenger RNA expression. The results were as follows. (1) Morphologically, trimethyltin produced a progressive loss of hippocampal CA3 and CA4 pyramidal cells, starting from four days after peroral treatment with trimethyltin hydroxide (9 mg/kg), as described previously. (2) Neurophysiologically, the increased seizure susceptibility to pentylenetetrazol treatment reached a maximum at four days post-trimethyltin and then declined after five days post-trimethyltin. The maximal seizure susceptibility at four days post-trimethyltin was confirmed by the immediate and long-lasting appearance of spike discharge in the hippocampus. However, this was not verified by the expression of c-fos messenger RNA in the hippocampus, which was comparable between trimethyltin-treated and control rats. (3) Behaviorally, the time-courses of aggression and learning impairment were similar to that of the seizure susceptibility. (4) Neurochemically, trimethyltin treatment caused changes of neurochemical markers, which were manifested by the elevation of neuropeptide Y content in the entorhinal cortex, and of choline acetyltransferase in the hippocampal CA3 subfield. Trimethyltin may offer potential as a tool for investigations on the relationship between neuronal death in the hippocampus and the development of seizure susceptibility and learning impairment. Alterations in glucocorticoids, glutamate and neuropeptides may all contribute to the manifestation of the trimethyltin syndrome.

Topics: Animals; Brain Chemistry; Choline O-Acetyltransferase; Corticotropin-Releasing Hormone; Disease Models, Animal; Electroencephalography; Hippocampus; Immunohistochemistry; In Situ Hybridization; Learning; Male; Maze Learning; Memory; Neurodegenerative Diseases; Neuropeptide Y; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Seizures; Somatostatin; Trimethyltin Compounds

Neuropeptide Y (NPY) inhibits excitatory synaptic transmission in the hippocampus and is implicated in control of limbic seizures. In the present study, we examined hippocampal function and the response to pharmacologically induced seizures in mutant mice lacking this peptide. In slice electrophysiology studies, no change in normal hippocampal function was observed in NPY-deficient mice compared with normal wild-type littermates. Kainic acid (KA) produced limbic seizures at a comparable latency and concentration in NPY-deficient mice compared with littermates. However, KA-induced seizures progressed uncontrollably and ultimately produced death in 93% of NPY-deficient mice, whereas death was rarely observed in wild-type littermates. Intracerebroventricular NPY infusion, before KA administration, prevented death in NPY-deficient mice. These results suggest a critical role for endogenous NPY in seizure control.

Topics: Action Potentials; Animals; Convulsants; Electroencephalography; Epilepsy; Gene Expression Regulation; Genotype; Hippocampus; Kainic Acid; Mice; Mice, Knockout; Neuropeptide Y; Perforant Pathway; Seizures; Synaptic Transmission

Rats treated with kainic acid develop limbic seizures and have elevated levels of circulating catecholamines resulting from an extensive stimulation of the adrenal gland. We investigated the levels of several constituents of chromaffin granules in rat adrenal medulla after injection of kainic acid. This treatment increased mRNA steady-state levels of enkephalin, neuropeptide Y and chromogranin B 2-6-fold. Elevated levels of these constituents were found as early as 2 h after treatment and lasted up to 24 h. Chromogranin A and secretogranin II mRNA levels, on the other hand, remained unchanged. Adrenal catecholamine concentrations were reduced by 80%. Pre-treatment of rats with thiopental prior to kainic acid prevented seizures, the decline in catecholamines and the elevation of enkephalin and neuropeptide Y mRNAs but not that of chromogranin B. On the other hand, the peripherally acting ganglionic blocker chlorisondamine did not protect from the kainic acid-induced up-regulation of chromogranin B mRNA, suggesting that chromogranin B mRNA may be regulated by a direct effect of kainic acid on chromaffin cells. The pattern of changes in mRNA expression differed from that seen after insulin hypoglycemia or reserpine treatment. Thus, stimulation of the splanchnic innervation in vivo by various means leads to an individual and independent regulation of granule constituents by quite different mechanisms.

Topics: Adrenal Medulla; Animals; Chromogranin A; Chromogranins; Enkephalins; Epinephrine; Gene Expression Regulation; Kainic Acid; Kinetics; Limbic System; Male; Neuropeptide Y; Norepinephrine; Protein Biosynthesis; Proteins; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures; Thiopental; Transcription, Genetic

Neuropeptide Y (NPY), a 36-amino-acid transmitter distributed throughout the nervous system, is thought to function as a central stimulator of feeding behaviour. NPY has also been implicated in the modulation of mood, cerebrocortical excitability, hypothalamic-pituitary signalling, cardiovascular physiology and sympathetic function. However, the biological significance of NPY has been difficult to establish owing to a lack of pharmacological antagonists. We report here that mice deficient for NPY have normal food intake and body weight, and become hyperphagic following food deprivation. Mutant mice decrease their food intake and lose weight, initially to a greater extent than controls, when treated with recombinant leptin. Occasional, mild seizures occur in NPY-deficient mice and mutants are more susceptible to seizures induced by a GABA (gamma-aminobutyric acid) antagonist. These results indicate that NPY is not essential for certain feeding responses or leptin actions but is an important modulator of excitability in the central nervous system.

Topics: Animals; Body Weight; Eating; Feeding Behavior; Female; Food Deprivation; GABA Antagonists; Gene Targeting; Humans; Hyperphagia; Leptin; Male; Mice; Neuropeptide Y; Pentylenetetrazole; Proteins; Seizures

Induction of c-fos mRNA and Fos was studied in the hilus and granular layer of the dentate gyrus at various times up to 24 h after single electroconvulsive stimulation (ECS) using in situ hybridization and immunocytochemistry. In both areas of the dentate gyrus, a prominent induction of c-fos mRNA and Fos was observed. Compared to the granular layer, however, c-fos mRNA and Fos in hilar cells reached maximum later and remained elevated considerably longer. Several neurochemically distinct populations of hilar neurons have been described, some of which contain neuropeptide Y (NPY) and/or somatostatin (SS). Using double-labelling immunocytochemistry, we examined to what extent Fos was induced in these hilar neurons after ECS. Although a minor population of non-NPY non-SS cells displayed Fos induction early after ECS, prolonged induction of Fos almost exclusively occurred in NPY or SS neurons. The Fos-immunoreactive NPY or SS neurons only amounted to about 50% of the total hilar population of NPY or SS neurons. The present observations suggest that a subpopulation of hilar NPY and SS neurons may be central to the actions of electroconvulsive seizures in the dentate gyrus.

Topics: Animals; Dentate Gyrus; Electric Stimulation; Immunohistochemistry; In Situ Hybridization; Male; Neurons; Neuropeptide Y; Oligonucleotide Probes; Proto-Oncogene Proteins c-fos; Rats; Rats, Wistar; RNA, Messenger; Seizures; Somatostatin

The effects of intracerebroventricular neuropeptide Y (NPY) or somatostatin were studied upon hippocampal EEG seizures elicited by electrical stimulation of the rat dentate gyrus or subiculum. At doses of 6 and 12 nmol, the latter dose being more effective, NPY reduced the primary afterdischarge duration (1.ADD) and almost completely abolished the secondary afterdischarge. The reduction in 1.ADD resulted from an increase in afterdischarge threshold. The reduction in secondary afterdischarge duration was independent of a reduction in 1.ADD. This implies that NPY not only exerts antiepileptiform effects in the dentate gyrus and subiculum, but also in areas to which epileptiform EEG activity spreads before reverberating. In addition, NPY strongly reduced seizure-related 'wet dog shakes' (WDS). This is consistent with previous studies showing that the dentate gyrus is essential for the generation of WDS. However, NPY inhibited WDS even when 1.ADDs were evoked which did not differ from those of vehicle rats, indicating extra-dentate inhibition by NPY as well. No effects were seen with somatostatin. These results show that NPY exerts antiepileptiform effects in vivo, suggesting that increased NPY in the hippocampal formation observed after seizures is a compensatory anti-seizure response.

Topics: Animals; Behavior, Animal; Dentate Gyrus; Electric Stimulation; Electroencephalography; Hippocampus; Injections, Intraventricular; Male; Neuropeptide Y; Rats; Rats, Wistar; Seizures

Using immunocytochemistry and in situ hybridization analysis of mRNA, we investigated the changes in the expression of somatostatin and neuropeptide Y (NPY) in the rat hippocampal principal neurons in kindling or after electrically induced status epilepticus (SE), two models of limbic epilepsy associated with different chronic sequelae of seizures and seizure-related neuropathology. At the preconvulsive stage 2 of kindling and after three consecutive tonic-clonic seizures (stage 5) but not after a single-discharge (AD), somatostatin and NPY immunoreactivity (IR) were markedly increased in interneurons of the deep hilus and the polymorphic cell layer and their presumed projections to the outer molecular layer of the dentate gyrus. Increased mRNA levels were observed in the same neurons. NPY IR and mRNA were highly expressed in pyramidal-shaped basket cells at both stages of kindling. IR was similar two days after stages 2 or 5 of kindling while less pronounced effects were observed one week after kindling completion. Peptide-containing neurons in the hilus appeared well preserved in spite of an average of 24% reduction of Nissl stained cells (p < 0.01) in the stimulated and contralateral hippocampus at stage 5. No sprouting of mossy fibres in the inner molecular layer was found as assessed by Timm staining. Thirty days after SE, somatostatin IR was slightly reduced or similar to controls in the ventral dentate gyrus and molecular layer in four or six rats (SE-I group) while in the two other post-SE rats (SE-II), somatostatin IR was lost. These changes were associated with a different extent of neurodegeneration as assessed by cell counting of Nissl stained sections. In the granule cells/mossy fibres NPY-IR was transiently expressed at stage 2 and after a single AD. Differently, NPY-IR was persistently enhanced in the mossy fibres of all post-SE rats particularly in the SE-II group. In these rats, NPY immunoreactive fibres were detected in the infrapyramidal region of the stratum oriens CA3 and in the inner molecular layer of the dentate gyrus very likely labeling sprouted mossy fibres. In the hippocampus proper of kindled rats, somatostatin and NPY IR were respectively enhanced in the stratum lacunosum moleculare, the subiculum and in the alveus while no significant changes were observed after SE. Changes in peptide expression were bilateral and involved both the dorsal and the ventral hippocampus. The lasting modifications in peptides IR and mRNA expressi

Topics: Animals; Dentate Gyrus; Functional Laterality; Hippocampus; Immunohistochemistry; Kindling, Neurologic; Limbic System; Nerve Degeneration; Neuronal Plasticity; Neurons; Neuropeptide Y; Rats; RNA, Messenger; Seizures; Somatostatin

Topics: Animals; In Situ Hybridization; Kindling, Neurologic; Limbic System; Male; Neurons; Neuropeptide Y; Protein Precursors; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures; Somatostatin

Stargazer mutant mice inherit a recessive neuronal excitability phenotype featuring frequent non-convulsive spike-wave seizures that arise from synchronous bursting in neocortical, thalamic and hippocampal networks. Immunocytochemistry reveals that granule cells in the mutant dentate gyrus aberrantly express neuropeptide Y (NPY) at multiple ages following the developmental onset of seizures. The ectopic NPY is selectively concentrated in the mossy fibers, co-localizing with the releasable dense core vesicle pool. The NPY content of native NPY+local circuit neurons is also elevated in the mutant CNS. There is no concurrent elevation of hippocampal 72 kDa heat shock protein (HSP72), glial fibrillary acidic protein (GFAP) or NADPH-diaphorase, three markers that are induced during cellular injury, and no evidence of granule cell loss. Since mossy fiber NPY expression appears after the developmental onset of spike-wave discharges and can be induced in wild type granule cells by electrical stimulation, the altered peptide phenotype is likely to reflect transynaptic gene induction triggered by synchronous bursting. These results link a specific pattern of repetitive synaptic input with selective molecular plasticity in dentate granule cells that may contribute to dynamic modifications in hippocampal network excitability.

Topics: Action Potentials; Age of Onset; Animals; Cell Count; Cortical Synchronization; Gene Expression Regulation; Mice; Mice, Neurologic Mutants; Nerve Fibers; Neurons; Neuropeptide Y; Phenotype; Point Mutation; Seizures; Subcellular Fractions; Transcriptional Activation

We measured the release of neuropeptide Y (NPY) from hippocampal slices of rats at various times after limbic seizures induced by a subcutaneous injection of 12 mg/kg kainic acid (KA). Two days after KA, 100 mM KCl induced a 1.6 +/- 0.2-fold increase in NPY release compared to saline-injected rats (P < 0.05), while spontaneous and 50 mM KCl-induced release were unchanged. Thirty days after KA, the spontaneous and 100 mM KCl-induced efflux of NPY was enhanced 2-fold on average (P < 0.01) compared to controls, while no significant differences were found using 50 mM KCl. Tissue concentration of NPY was raised 2.2 +/- 0.2 times (P < 0.01) 30 days after KA. Thirty days after KA, the rats showed enhanced susceptibility to tonic-clonic seizures, assessed using a normally subconvulsive dose of pentylenetetrazol (PTZ; 30 mg/kg). A selective antibody (Ab) raised against NPY in a rabbit was infused bilaterally for three days in the CA3 area and dentate gyrus (DG) of the dorsal hippocampus of rats treated 30 days before with KA. This significantly reduced (P < 0.05) the number of animals with tonic-clonic seizures induced by 30 mg/kg PTZ, compared to KA treated rats which received the inactivated Ab. The Ab was ineffective in naive rats injected with a full convulsive dose of PTZ (55 mg/kg). The present results show that neuronal release of NPY is enhanced in the hippocampus after limbic seizures induced in rats by KA. This effect persists for at least 30 days and may contribute to the chronically enhanced susceptibility to seizures after injection of this toxin.

Topics: Animals; Antibodies; Chronic Disease; Disease Susceptibility; Dose-Response Relationship, Drug; Electrophysiology; Hippocampus; In Vitro Techniques; Kainic Acid; Male; Neurons; Neuropeptide Y; Pentylenetetrazole; Potassium Chloride; Rats; Rats, Sprague-Dawley; Seizures

Using in situ hybridization histochemistry neuropeptide Y (NPY) mRNA expression was investigated after intraperitoneal injection of kainic acid (KA) and after local application of KA or quinolinic acid into the dentate gyrus of the rat. Enhanced concentrations of NPY mRNA were observed in interneurons of the hilus, including presumptive fusiform neurons and pyramidal-shaped basket cells already 4 hours after initiation of limbic seizures by KA (10 mg/kg, i.p.). Increased NPY expression persisted in neurons resistant to seizure-induced cell death (6-48 h after i.p. KA). Exceptionally high hybridization signals were found in interneurons of the hilus and the CA1 and CA3 sectors 8 months after KA-induced limbic seizures. In the granule cell layer only a transient but pronounced increase in NPY mRNA was observed 12-24 h after injection. Only moderate changes were observed in this cell layer at later intervals. Anticonvulsant treatment with thiopental, after a brief period of generalized seizures, prevented the increase in NPY mRNA in granule cells but not in interneurons. No change in NPY message was found also in granule cells of rats which responded with mild "wet dog shake" behavior but not with motor seizures to KA injection. Local injections of low doses of KA (0.05-0.2 nmol) or quinolinic acid (6.5-100 nmol) into the dentate gyrus of the hippocampus under deep thiopental anesthesia, after 24 h, resulted in increased concentrations of NPY message in interneurons of the ipsilateral, but not of the contralateral hilus and not in granule cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Gene Expression; Hippocampus; In Situ Hybridization; Interneurons; Kainic Acid; Kinetics; Male; Neuropeptide Y; Quinolinic Acid; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures

Previous studies have shown that neuropeptide mRNA expression is altered in the dentate gyrus, and pyriform, entorhinal and perirhinal cortices following amygdala kindling. However, because rats were kindled every day and some mRNA alterations last longer than 24 h, a true measure of the alterations induced by a single seizure was confounded by the previous day's seizure. To circumvent this problem, rats were fully kindled, had six days without stimulation, and then were given one more seizure. Rats were sacrificed either 4 h, 24 h or 4 days after this last seizure. The levels of mRNAs for TRH, NPY and ENK were measured in the dentate gyrus and limbic cortices. Four hours after a seizure, TRH and NPY mRNAs were maximally increased in the dentate gyrus granule layer, but returned to baseline levels by 24 h. In contrast, 4 h after a seizure, TRH and NPY mRNAs were not, or only slightly, increased in the pyriform, entorhinal and perirhinal cortices, but significantly elevated 24 h after a seizure. ENK mRNA was increased both 4 and 24 h after a seizure in the pyriform, entorhinal and perirhinal cortices but showed no increases in the dentate gyrus at any time. By 4 days, peptide mRNA levels returned to baseline, except for ENK mRNA in the pyriform cortex. These results demonstrate a non-uniform and complex pattern of peptide mRNA expression following an amygdala kindled seizure. They further suggest that regional and time course differences in gene transcription and expression may be important factors in understanding both the transient, adaptive anticonvulsant and longer lasting proconvulsant effects of these neuropeptides.

Topics: Amygdala; Animals; Base Sequence; Enkephalins; Gene Expression Regulation; Kindling, Neurologic; Male; Molecular Sequence Data; Nerve Tissue Proteins; Neuropeptide Y; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures; Thyrotropin-Releasing Hormone; Time Factors

Electroconvulsive seizures (ECS) increase tyrosine hydroxylase (TH) activity in the locus coeruleus (LC) but not in the substantia nigra (SN). To determine whether new enzyme synthesis contributes to the increase in TH activity, we carried out in situ hybridization histochemistry to determine the effect of ECS on TH mRNA levels in the LC and SN. The effect of ECS on neuropeptide Y (NPY) mRNA levels in the LC was also studied because NPY coexists with norepinephrine in the LC neurons and has been implicated in depressive disorders. A significant increase was observed in TH mRNA and NPY mRNA levels in LC neurons in the ECS group. There was no difference between TH or NPY mRNA levels in the left and right LC. No change was observed in TH mRNA expression in the SN compacta or SN reticulata. We conclude that the regionally selective increase in TH activity after ECS is at least partly due to increased gene expression and that NPY gene expression is regulated in a similar fashion following ECS.

Topics: Animals; Electroshock; Enzyme Induction; Gene Expression Regulation; In Situ Hybridization; Locus Coeruleus; Male; Nerve Tissue Proteins; Neuropeptide Y; Rats; Rats, Sprague-Dawley; RNA, Messenger; Seizures; Substantia Nigra; Tyrosine 3-Monooxygenase

Neuroanatomical methods were used to determine if cocaine irreversibly injures neurons. Despite acute and chronic high-dose treatments for months that produced stereotyped behavior and seizures, and the use of a sensitive silver impregnation method, we were unable to find any evidence of neuronal damage anywhere in the brain. Since expression of the inducible 72 kDa heat shock protein (HSP72) is a sensitive indicator of potentially toxic neuronal stress, we next determined if cocaine evoked HSP72 expression. Even high doses of cocaine that evoked seizures did not induce HSP72 immunoreactivity anywhere within the brain, whereas kainic acid produced widespread HSP72 immunoreactivity and irreversible injury. Having failed to find indications of frank neurotoxicity, we examined peptide and protein cell marker immunoreactivities in search of cocaine-induced changes. Although cocaine treatment had no obvious effects on the patterns of hippocampal calbindin-D28K, somatostatin-, tyrosine hydroxylase- and parvalbumin immunoreactivities, cocaine reliably altered neuropeptide Y-like immunoreactivity (NPY-LI). Most notably, NPY-LI was expressed in hippocampal dentate granule cells and pyriform cortical neurons, which do not normally express it. Conversely, we noted decreased NPY-LI in dentate hilar neurons that normally do express it. Since both changes in NPY-LI were seen only in cocaine-treated rats that exhibited seizures, the role of seizure activity per se in producing the NPY changes was addressed in normal rats by electrical stimulation of the perforant path. Like cocaine, perforant path stimulation for as little as 15min evoked NPY-LI in granule cells but did not replicate the cocaine-induced decrease in hilar cell NPY-LI. These results suggest that cocaine does not irreversibly injure neurons in the rat, even at doses that induce seizures. However, cocaine produces long-lasting changes in NPY expression that are of unknown functional significance. Our inability to demonstrate cocaine-induced neuronal damage in rats should in no way be taken as evidence of its safety in humans.

Topics: Animals; Cocaine; Drug Administration Schedule; Hippocampus; Immunohistochemistry; Male; Nerve Degeneration; Neurons; Neuropeptide Y; Neurotoxins; Rats; Rats, Sprague-Dawley; Seizures; Silver; Stereotyped Behavior; Time Factors

We studied the effects of modification of duration of seizures induced by electroconvulsive stimuli (ECS) on the changes in concentration of neuropeptide Y (NPY), neurokinin A (NKA), substance P (SP) and neurotensin (NT)-like immunoreactivity (-LI) in specific rat brain regions. Rats were divided into groups pretreated with saline, indomethacin, flurbiprofen or diazepam prior to either six sham ECSs or six ECSs. After sacrifice by focused microwave irradiation, brains were dissected into frontal cortex, occipital cortex, striatum, hippocampus, pituitary and hypothalamic sections. Peptides were extracted and measured in extract aliquots by specific radioimmunoassays. Repeated ECS increased NPY-LI and NKA-LI in the hippocampus and the occipital cortex. No effect on SP-LI or NT-LI was found. Indomethacin and flurbiprofen had no effect on the tonic seizure time following ECS, and they did not affect the ECS-induced alterations of the brain peptides. Diazepam pretreatment decreased the tonic seizure time following ECS in a dose-dependent manner. However, diazepam did not modify the ECS-induced increase in NPY-LI and NKA-LI concentrations. The results firmly establish that ECS leads to specific peptide increases in discrete rat brain regions and raise the possibility that such changes may not entirely be a consequence of seizures per se.

Topics: Animals; Brain; Diazepam; Eicosanoids; Electroshock; Male; Neurokinin A; Neuropeptide Y; Neuropeptides; Neurotensin; Rats; Rats, Sprague-Dawley; Seizures; Substance P; Time Factors; Tissue Distribution

The influence of sustained epileptic seizures evoked by intraperitoneal injection of kainic acid on the gene expression of the neuropeptides somatostatin and neuropeptide Y and on the damage of neurons containing these peptides was studied in the rat brain. Injection of kainic acid induced an extensive loss of somatostatin and, though less pronounced, of neuropeptide Y neurons in the inner part of the hilus of the dentate gyrus. Neuropeptide Y-immunoreactive neurons located in the subgranular layer of the hilus, presumably pyramidal-shaped basket cells, were spared by the treatment. Although neuropeptide Y messenger RNA was not detected in granule cells of control rats, it was found there after kainic acid seizures at all time intervals investigated (12 h to 90 days after injection of kainic acid). High concentrations of neuropeptide Y messenger RNA were especially observed 24 h after injection of kainic acid. At this time neuropeptide Y messenger RNA was also transiently observed in CA1 pyramidal cells. Neuropeptide Y synthesis in granule cells in turn gave rise to an intense immunoreactivity of the peptide in the terminal field of mossy fibers which persisted for the entire time period (90 days) investigated. In addition, neuropeptide Y messenger RNA concentrations were also drastically elevated in presumptive basket cells located at the inner surface of the granule cell layer, especially at the "late" time intervals investigated (30-90 days after kainic acid). These data support the concept that extensive activation of granule cells by limbic seizures contributes to the observed neuronal cell death in CA3 pyramidal neurons and interneurons of the hilus. Consecutively, basket cells containing neuropeptide Y and presumably GABA might be activated and participate in recurrent inhibition of granule cells. Neuropeptide Y-immunoreactive fibers observed in the inner molecular layer at "late" time intervals after kainic acid may result either from collateral sprouting of mossy fibers or from basket cells extensively expressing the peptide. It is speculated that neuropeptide Y synthesized and released at a high rate from granule cells and basket cells may exert a protective action against seizures.

Topics: Animals; Hippocampus; Immunohistochemistry; In Situ Hybridization; Kainic Acid; Kindling, Neurologic; Limbic System; Male; Neurons; Neuropeptide Y; Pentylenetetrazole; Rats; Rats, Sprague-Dawley; Seizures; Somatostatin

A selective loss of somatostatin- and neuropeptide Y-immunoreactive neurons has been reported in the dentate gyrus of rats with cerebral ischemia, following sustained electric stimulation, and in patients with non-tumor-related temporal lobe epilepsy. Three theoretical possibilities were tested that may explain why these neurons are more vulnerable than others, such as the cholecystokinin- and calcium-binding protein-containing cells: (1) the seizure-sensitive neurons are more involved in specific excitatory circuitry than are the seizure-resistant cells; (2) the somatostatin- and neuropeptide Y-immunoreactive neurons are less protected by inhibitory GABAergic inputs than cells immunoreactive for cholecystokinin; and (3) the seizure-sensitive neurons do not contain calcium-binding proteins. The present results of light and electron microscopic, single and double, immunostaining experiments and co-localization studies performed on the hippocampal formations of rats and non-human primates, support the idea that the calcium-binding protein content of a neuron defines its seizure sensitivity.

Topics: Animals; Brain Mapping; Calcium-Binding Proteins; Chlorocebus aethiops; Cholecystokinin; Cytoplasmic Granules; Epilepsy, Temporal Lobe; Female; gamma-Aminobutyric Acid; Hippocampus; Male; Microscopy, Electron; Neural Inhibition; Neurons; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Rats, Wistar; Seizures; Somatostatin; Synapses; Synaptic Transmission

The levels of preproneuropeptide Y (ppNPY) mRNA and preprosomatostatin (ppSOM) mRNA were analyzed in different brain regions during the development of hippocampal kindling in rats. ppNPY mRNA levels were markedly elevated in the dorsal hippocampus bilaterally, two days after stage 2 (preconvulsive stage) and stage 5 (full seizure expression). The contents of ppSOM mRNA were slightly, although not significantly, increased in the dorsal hippocampus at stage 2 whereas a significant increase was observed in the ipsilateral hippocampus of fully kindled rats. ppNPY and ppSOM mRNA levels were unchanged in the cortex and striatum at both stages of kindling. These results show that an increased synthesis of somatostatin and neuropeptide Y, with a greater effect for the latter, occurs during hippocampal kindling in rats. The relative role of the two peptides in the development and expression of kindling phenomenon remains to be elucidated.

Topics: Animals; Blotting, Northern; Electroencephalography; Hippocampus; Kindling, Neurologic; Male; Neuropeptide Y; Protein Precursors; Rats; Reference Values; RNA, Messenger; Seizures; Somatostatin

Recent studies have shown marked increases in brain content of neuropeptide Y (NPY) after seizures induced by intraperitoneal injection of kainic acid and after pentylenetetrazole kindling in the rat. We have now investigated possible changes in the rate of biosynthesis of NPY after kainic acid treatment, by using pulse-labeling of the peptide and by determining prepro-NPY mRNA concentrations. For pulse labeling experiments, [3H]tyrosine was injected into the frontal cortex, and the incorporation of the amino acid into NPY was determined after purifying the peptide by gel filtration chromatography, antibody affinity chromatography, and reversed-phase HPLC. At 2 and 30 days after kainic acid treatment, the rate of tyrosine incorporation was enhanced by approximately 380% in the cortex. In addition, concentrations of pre-pro-NPY mRNA were determined in four different brain areas by hybridization of Northern blots with a complementary 32P-labeled RNA probe 2, 10, 30, and 60 days after kainic acid treatment. Marked increases were observed in the frontal cortex (by up to 350% of controls), in the dorsal hippocampus (by 750%), and in the amygdala/pyriform cortex (by 280%) at all intervals investigated. In the striatum only a small, transient increase was observed. The data demonstrate increased expression of prepro-NPY mRNA and an enhanced rate of in vivo synthesis of NPY as a result of seizures induced by the neurotoxin kainic acid.

Topics: Amygdala; Animals; Brain; Chromatography, High Pressure Liquid; Corpus Striatum; Frontal Lobe; Gene Expression; Hippocampus; Kainic Acid; Male; Neuropeptide Y; Nucleic Acid Hybridization; Protein Precursors; Rats; Rats, Inbred Strains; RNA, Messenger; Seizures; Tritium; Tyrosine

The influence of anticonvulsant treatment upon (1) chronically increased seizure susceptibility, (2) on late increases in peptide levels and (3) on seizure-induced brain damage was investigated during various stages of acute kainic acid (10 mg/kg i.p.)-induced seizures. The seizures were interrupted at various stages of the syndrome (50 min to 24 h after injection of the toxin) by injecting thiopental (50 mg/kg i.p.) or the excitatory amino acid antagonist, MK-801 (10 mg/kg i.p.). The increase in neuropeptide Y and somatostatin levels in the frontal cortex could be prevented by early injection of either anticonvulsant (up to 180 min after kainic acid). No protection against the increase in peptide levels was observed when the anticonvulsants were applied later. Kainic acid-induced neuronal damage in the amygdala, with glutamate decarboxylase as a neurochemical marker, was entirely prevented by interrupting seizures up to 2 h after kainic acid. Partial protection (about 40-50%) was even found when the anticonvulsant treatment was applied after the acute syndrome, as late as 8 h after kainic acid injection. Chronically increased seizure susceptibility induced by kainic acid was not prevented, even by early injection (90 min after kainic acid) of the anticonvulsant drugs. The data indicate that (1) the late increase in seizure susceptibility may be initiated early after injection of kainic acid. (2) the late increase in peptide levels may be related to the frequency of acute seizures rather than to a change in seizure threshold or brain damage and (3) even late anticonvulsant therapy may antagonize seizure-induced brain damage in the amygdala.

Topics: Animals; Anticonvulsants; Brain; Brain Chemistry; Dibenzocycloheptenes; Dizocilpine Maleate; Glutamate Decarboxylase; Kainic Acid; Male; Neuropeptide Y; Neuropeptides; Pentylenetetrazole; Rats; Rats, Inbred Strains; Seizures; Somatostatin

The Mongolian gerbil, with its spontaneous epileptiform seizures, was chosen as an experimental model of human epilepsy. Neurochemical parameters possibly related to the seizure process were studied. In the immediate seizure process amino acid profiles of cortex, hippocampus, and striatum were not different in seizuring animals when compared to seizure-resistance controls. Of two peptides analyzed, only somatostatin appeared elevated in the cortex 2 hr postictal (143 fmol/mg protein; controls, 123 fmol/mg protein); neuropeptide Y was not affected. A follow up of the time course of cyclic AMP and cyclic GMP showed significant elevations of both substances as a consequence of seizures. Most prominent was a 5.5-fold increase in cyclic GMP in the cerebellum 30 sec after seizure onset.

Topics: Amino Acids; Animals; Brain; Disease Models, Animal; Female; Gerbillinae; Male; Neuropeptide Y; Nucleotides, Cyclic; Seizures; Somatostatin; Time Factors