phenylalanine-methyl-ester and Disease-Models--Animal

Phenylketonuria (PKU) is the most common inborn error of amino acid metabolism. Usually diagnosed within the first month of birth, it is essential that the patient strictly follow the dietary restriction of natural protein intake. Otherwise, PKU impacts the development of the brain severely and may result in microcephaly, epilepsy, motor deficits, intellectual disability, and psychiatric and behavioral disorders. The neuropathology associated with PKU includes defects of myelination, insufficient synthesis of monoamine neurotransmitters, amino acid imbalance across the blood-brain barrier, and involves intermediary metabolic pathways supporting energy homeostasis and antioxidant defenses in the brain. Considering that the production of reactive oxygen species (ROS) is inherent to energy metabolism, we investigated the association of creatine+pyruvate (Cr + Pyr), both energy substrates with antioxidants properties, as a possible treatment to mitigate oxidative stress and phosphotransfer network impairment elicited in the brain of young Wistar rats by chemically-induced PKU. We induced PKU through the administration of α-methyl-L-phenylalanine and phenylalanine for 7 days, with and without Cr + Pyr supplementation, until postpartum day 14. The cotreatment with Cr + Pyr administered concurrently with PKU induction prevented ROS formation and part of the alterations observed in antioxidants defenses and phosphotransfer network enzymes in the cerebral cortex, hippocampus, and cerebellum. If such prevention also occurs in PKU patients, supplementing the phenylalanine-restricted diet with antioxidants and energetic substrates might be beneficial to these patients.

Topics: Animals; Antioxidants; Blood-Brain Barrier; Brain; Creatine; Disease Models, Animal; Energy Metabolism; Oxidative Stress; Phenylalanine; Phenylketonurias; Pyruvic Acid; Rats; Rats, Wistar; Reactive Oxygen Species

We previously reported that the investigational multimodal antidepressant, vortioxetine, reversed 5-HT depletion-induced memory deficits while escitalopram and duloxetine did not. The present report studied the effects of vortioxetine and the potential impact of its 5-HT1A receptor agonist and 5-HT3 receptor antagonist properties on 5-HT depletion-induced memory deficits. Recognition and spatial working memory were assessed in the object recognition (OR) and Y-maze spontaneous alternation (SA) tests, respectively. 5-HT depletion was induced in female Long-Evans rats using 4-cholro-DL-phenylalanine methyl ester HCl (PCPA) and receptor occupancies were determined by ex vivo autoradiography. Rats were acutely dosed with vortioxetine, ondansetron (5-HT3 receptor antagonist) or flesinoxan (5-HT1A receptor agonist). The effects of chronic vortioxetine administration on 5-HT depletion-induced memory deficits were also assessed. 5-HT depletion reliably impaired memory performance in both the tests. Vortioxetine reversed PCPA-induced memory deficits dose-dependently with a minimal effective dose (MED) ≤0.1mg/kg (∼80% 5-HT3 receptor occupancy; OR) and ≤3.0mg/kg (5-HT1A, 5-HT1B, 5-HT3 receptor occupancy: ∼15%, 60%, 95%) in SA. Ondansetron exhibited a MED ≤3.0μg/kg (∼25% 5-HT3 receptor occupancy; OR), but was inactive in the SA test. Flesinoxan had a MED ≤1.0mg/kg (∼25% 5-HT1A receptor occupancy; SA); only 1.0mg/kg ameliorated deficits in the NOR. Chronic p.o. vortioxetine administration significantly improved memory performance in OR and occupied 95%, 66%, and 9.5% of 5-HT3, 5-HT1B, and 5-HT1A receptors, respectively. Vortioxetine's effects on SA performance may involve 5-HT1A receptor agonism, but not 5-HT3 receptor antagonism, whereas the effects on OR performance may involve 5-HT3 receptor antagonism and 5-HT1A receptor agonism.

Topics: 8-Hydroxy-2-(di-n-propylamino)tetralin; Animals; Benzamides; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Indazoles; Maze Learning; Memory Disorders; Memory, Short-Term; Phenylalanine; Piperazines; Protein Binding; Pyridines; Rats; Rats, Long-Evans; Receptor, Serotonin, 5-HT1A; Receptors, Serotonin, 5-HT3; Recognition, Psychology; Serotonin 5-HT1 Receptor Agonists; Serotonin 5-HT3 Receptor Antagonists; Sulfides; Time Factors; Tritium; Tropanes; Vortioxetine

Depressed patients suffer from cognitive dysfunction, including memory deficits. Acute serotonin (5-HT) depletion impairs memory and mood in vulnerable patients. The investigational multimodal acting antidepressant vortioxetine is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, 5-HT1B receptor partial agonist, 5-HT1A receptor agonist and 5-HT transporter (SERT) inhibitor that enhances memory in normal rats in novel object recognition (NOR) and conditioned fear (Mørk et al., 2013). We hypothesized that vortioxetine's 5-HT receptor mechanisms are involved in its memory effects, and therefore investigated these effects in 5-HT depleted rats. Four injections of the irreversible tryptophan hydroxylase inhibitor 4-chloro-dl-phenylalanine methyl ester hydrochloride (PCPA, 86mg/kg, s.c.) induced 5-HT depletion, as measured in hippocampal homogenate and microdialysate. The effects of acute challenge with vortioxetine or the 5-HT releaser fenfluramine on extracellular 5-HT were measured in PCPA-treated and control rats. PCPA's effects on NOR and spontaneous alternation (SA) performance were assessed along with the effects of acute treatment with 5-hydroxy-l-tryptophan (5-HTP), vortioxetine, the selective 5-HT reuptake inhibitor escitalopram, or the 5-HT norepinephrine reuptake inhibitor duloxetine. SERT occupancies were estimated by ex vivo autoradiography. PCPA depleted central 5-HT by >90% in tissue and microdialysate, and impaired NOR and SA performance. Restoring central 5-HT with 5-HTP reversed these deficits. At similar SERT occupancies (>90%) vortioxetine, but not escitalopram or duloxetine, restored memory performance. Acute fenfluramine significantly increased extracellular 5-HT in control and PCPA-treated rats, while vortioxetine did so only in control rats. Thus, vortioxetine restores 5-HT depletion impaired memory performance in rats through one or more of its receptor activities.

Topics: 5-Hydroxytryptophan; Animals; Carbidopa; Citalopram; Disease Models, Animal; Dose-Response Relationship, Drug; Duloxetine Hydrochloride; Exploratory Behavior; Female; Hippocampus; Maze Learning; Memory Disorders; Phenylalanine; Piperazines; Protein Binding; Rats; Rats, Long-Evans; Recognition, Psychology; Selective Serotonin Reuptake Inhibitors; Serotonin; Sulfides; Thiophenes; Vortioxetine

Current treatments for depression, including serotonin-specific reuptake inhibitors (SSRIs), are only partially effective, with a high incidence of residual symptoms, relapse, and treatment resistance. Loss of cognitive flexibility, a component of depression, is associated with dysregulation of the prefrontal cortex. Reversal learning, a form of cognitive flexibility, is impaired by chronic stress, a risk factor for depression, and the stress-induced impairment in reversal learning is sensitive to chronic SSRI treatment, and is mimicked by serotonin (5-HT) depletion. Vortioxetine, a novel, multimodal-acting antidepressant, is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, a 5-HT1B receptor partial agonist, a 5-HT1A receptor agonist, and inhibits the 5-HT transporter. Using adult male rats, we first investigated the direct effects of vortioxetine, acting at post-synaptic 5-HT receptors, on reversal learning that was compromised by 5-HT depletion using 4-chloro-DL-phenylalanine methyl ester hydrochloride (PCPA), effectively eliminating any contribution of 5-HT reuptake blockade. PCPA induced a reversal learning impairment that was alleviated by acute or sub-chronic vortioxetine administration, suggesting that post-synaptic 5-HT receptor activation contributes to the effects of vortioxetine. We then investigated the effects of chronic dietary administration of vortioxetine on reversal learning that had been compromised in intact animals exposed to chronic intermittent cold (CIC) stress, to assess vortioxetine's total pharmacological effect. CIC stress impaired reversal learning, and chronic vortioxetine administration prevented the reversal-learning deficit. Together, these results suggest that the direct effect of vortioxetine at 5-HT receptors may contribute to positive effects on cognitive flexibility deficits, and may enhance the effect of 5-HT reuptake blockade.

Topics: Analysis of Variance; Animals; Anti-Anxiety Agents; Attention; Autoradiography; Body Weight; Cold Temperature; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Learning Disabilities; Male; Phenylalanine; Piperazines; Rats; Rats, Sprague-Dawley; Reversal Learning; Serotonin; Stress, Psychological; Sulfides; Vortioxetine

Changes in serotonin(2C) receptor (5-HTR2c) editing, splicing and density were found in conditions such as depression and suicide, but mechanisms explaining the changes in 5-HTR2c function are unknown. Thus, mice expressing only the fully edited VGV isoform of 5-HTR2c, in which clinically relevant behavioral changes are associated with alterations in splicing and receptor density, were studied. VGV mice displayed enhanced anxiety-like behavior in response to a preferential 5-HTR2c agonist in the social interaction test. Nearly half of interactions between pairs of VGV congeners consisted of fighting behaviors, whereas no fighting occurred in wild-type (WT) mice. VGV mice also exhibited a striking increase in freezing behaviors in reaction to an innately aversive ultrasonic stimulus. This behavioral phenotype occurred in conjunction with decreased brain 5-HT turnover during stress. These functional data were put in relation with the 5-HTR2c mRNA splicing process generating a truncated protein (5-HTR2c-Tr) in addition to the full-length receptor (5-HTR2c-Fl). 5-HTR2c-Tr mRNA was less abundant in many brain regions of VGV mice, which concomitantly had more 5-HTR2c than WT mice. Fluorescence resonance energy transfer and bioluminescence resonance energy transfer studies in transfected living HEK293T cells showed that 5-HTR2c-Tr interacts with 5-HTR2c-Fl. The 5-HTR2c-Tr was localized in the endoplasmic reticulum where it retained 5-HTR2c-Fl, preventing the latter to reach the plasma membrane. Consequently, 5-HTR2c-Tr decreased (3)H-mesulergine binding to 5-HTR2c-Fl at the plasma membrane in a concentration-dependent manner and more strongly with edited 5-HTR2c-Fl. These results suggest that 5-HTR2c pre-mRNA editing and splicing are entwined processes determining increased 5-HTR2c levels in pathological conditions through a deficit in 5-HTR2c-Tr.

Topics: Aggression; Animals; Anxiety; Bioluminescence Resonance Energy Transfer Techniques; Brain; Defense Mechanisms; Disease Models, Animal; Gene Expression Regulation; Glycine; HEK293 Cells; Humans; Hydroxyindoleacetic Acid; Interpersonal Relations; Mice; Mice, Inbred C57BL; Mutation; Phenylalanine; Protein Binding; Protein Isoforms; Receptor, Serotonin, 5-HT2C; RNA Editing; RNA Precursors; RNA Splicing; RNA, Messenger; Transfection; Ultrasonics; Valine

The administration of several compounds that can increase plasma phenylalanine levels and/or inhibit phenylalanine hydroxylase in rats was studied in order to determine their usefulness in inducing a phenylketonuria-like state. The results of this investigation revealed that 4.5 microns/10 g p-chlorophenylalanine is more effective than L-phenylalanine, alpha-methylphenylalanine, trimethoprim, Bactrim and Septra, since the former compound produced both adequate hyperphenylalaninemia and marked inhibition of hepatic phenylalanine hydroxylase activity. In addition, a 24-h study provided important insights into the changing diurnal patterns of specified biochemical parameters.

Topics: Animals; Disease Models, Animal; Drug Combinations; Female; Fenclonine; Phenylalanine; Phenylalanine Hydroxylase; Phenylketonurias; Rats; Rats, Inbred Strains; Sulfamethoxazole; Trimethoprim; Trimethoprim, Sulfamethoxazole Drug Combination