2C Receptor Research Articles

Molecular and behavioral responses of zebrafish embryos/larvae after sertraline exposure

Sertraline (SER) is one of the most frequently detected antidepressant drugs in aquatic environments. However, knowledge regarding SER-induced behavioral alterations in fish is insufficient, as well as the mechanisms underlying SER-induced toxicity. The present study aimed to determine behavioral and molecular responses in larval fish following SER exposure with a focus on its mode of action. Zebrafish embryos (~6 h-post-fertilization, hpf) were exposed to one of three concentrations of SER (1, 10, 100 μg/L) for 6 days, respectively. Evaluated parameters included development, behavior, transcripts related to serotonin signaling, serotonin levels, and acetylcholinesterase activity. Accelerated hatching of zebrafish embryos was observed for those fish exposed to 100 μg/L SER at 54 hpf. Locomotor activity (e.g. distance moved and mobile cumulative duration) was significantly reduced in larval zebrafish following exposure to 10 and 100 μg/L SER. Conversely, larval fish showed increased dark-avoidance after exposure to 1–100 μg/L SER. Of the measured transcripts related to serotonin signaling, only serotonin transporter (serta) and serotonin receptor 2c (5-ht2c) mRNA levels were increased in fish in response to 10 μg/L SER treatment. However, serotonin levels were unaltered in larvae exposed to SER. There were no differences among groups in acetylcholinesterase activity at any concentration tested. Taking together, the results evidenced that exposure to SER alters behavioral responses in early-staged zebrafish, which may be related to the abnormal expression of 5-ht2c. This study elucidates molecular responses to SER and characterizes targets that may be sensitive to antidepressant pharmaceuticals in larval fish.

Pharmacodynamic Gene Testing in Prader-Willi Syndrome.

Prader-Willi syndrome (PWS) is a rare genetic disorder with a complex neurobehavioral phenotype associated with considerable psychiatric co-morbidity. This clinical case series, for the first time, describes the distribution and frequency of polymorphisms of pharmacodynamic genes (serotonin transporter, serotonin 2A and 2C receptors, catechol-o-methyltransferase, adrenergic receptor 2A, methylene tetrahydrofolate reductase, and human leucocytic antigens) across the two major molecular classes of PWS in a cohort of 33 referred patients who met medical criteria for testing. When results were pooled across PWS genetic subtypes, genotypic and allelic frequencies did not differ from normative population data. However, when the genetic subtype of PWS was examined, there were differences observed across all genes tested that may affect response to psychotropic medication. Due to small sample size, no statistical significance was found, but results suggest that pharmacodynamic gene testing should be considered before initiating pharmacotherapy in PWS. Larger scale studies are warranted.

Molecular, biochemical and behavioural evidence for a novel oxytocin receptor and serotonin 2C receptor heterocomplex

The complexity of oxytocin-mediated functions is strongly associated with its modulatory effects on other neurotransmission systems, including the serotonin (5-hydroxytryptamine, 5-HT) system. Signalling between oxytocin (OT) and 5-HT has been demonstrated during neurodevelopment and in the regulation of specific emotion-based behaviours. It is suggested that crosstalk between neurotransmitters is driven by interaction between their specific receptors, particularly the oxytocin receptor (OTR) and the 5-hydroxytryptamine 2C receptor (5-HTR2C), but evidence for this and the downstream signalling consequences that follow are lacking. Considering the overlapping central expression profiles and shared involvement of OTR and 5-HTR2C in certain endocrine functions and behaviours, including eating behaviour, social interaction and locomotor activity, we investigated the existence of functionally active OTR/5-HTR2C heterocomplexes. Here, we demonstrate evidence for a potential physical interaction between OTR and 5-HTR2Cin vitro in a cellular expression system using flow cytometry-based FRET (fcFRET). We could recapitulate this finding under endogenous expression levels of both receptors via in silico analysis of single cell transcriptomic data and ex vivo proximity ligation assay (PLA). Next, we show that co-expression of the OTR/5-HTR2C pair resulted in a significant depletion of OTR-mediated Gαq-signalling and significant changes in receptor trafficking. Of note, attenuation of OTR-mediated downstream signalling was restored following pharmacological blockade of the 5-HTR2C. Finally, we demonstrated a functional relevance of this novel heterocomplex, in vivo, as 5-HTR2C antagonism increased OT-mediated hypoactivity in mice. Overall, we provide compelling evidence for the formation of functionally active OTR/5-HTR2C heterocomplexes, adding another level of complexity to OTR and 5-HTR2C signalling functionality.This article is part of the special issue on Neuropeptides.

The Role of 5-HT on Proplatelet Formation and Thrombopoietin Production

Background: Our previous work confirmed that serotonin (5-HT) promotes the proliferation of hemopoietic stem cells and megakaryocytes (Yang M et al, Stem Cells, 2007; 2014). However, the mechanisms remain indefinite. Methods: Q-PCR, Flow Cytometry, Western Blot, or Immunofluorescence microscope were used in the receptor and TPO study. MTT/CCK-8, Proplatelet assay, and Flow Cytometry were also used in cell proliferation and apoptosis study. The relationship between 5-HT and TPO was studied in a traumatic stress mice model. Results: In-vitro study, there was a stimulating effect of 5-HT on proplatelet formation in human bone marrow megakaryocytes. Human BM MK progenitors cultured in serum-free medium with either 5-HT (200nM) or TPO (100 ng/ml) had more proplatelet bearing MKs than the control group (5-HT (12.3 ± 5.0)% vs. Control (6.2 ± 3.5)%, P=0.025; TPO (15.6 ± 2.5)% vs. Control, P=0.04; n=4). The 5-HT treatment group showed more mature and more in the final stage MK cells as compared to the TPO group. 5-HT2A, 2B, 2C receptors were detected in the surface of megakaryocytes. The effect of 5-HT on proplatelet formation in MK cells was via 5-HT2 receptors and this effect was reduced by 5-HT2 receptor inhibitor ketanserin. 5-HT acted on cytoskeleton reorganization in MKs via 5-HT2 receptors and ERK1/2 pathway. Using an immunofluorescence microscope with F-actin specific binder rhodamine-phalloidin staining, the polymerized actin level was lower in the control group than the 5-HT group and actin distributed diffusely throughout the cytoplasm. In contrast, the polymerization actin level was higher in the 5-HT group. Adding ketanserin and ERK1/2 inhibitor PD98059 to 5-HT treatment, the fluorescence intensity was correspondingly reduced. Our data also demonstrated that ERK1/2 was activated in MKs treated with 5-HT for 30 minutes. In a traumatic stress mice model, both of 5-HT and TPO were increased, but the increasing of TPO is posterior to 5-HT. After added LX1606, the synthesis inhibitor of 5-HT, 5-HT was reduced markedly, as well as TPO. The expression of TPO mRNA and the production of TPO protein were increased as compared with the control in this model. Conclusions: This study suggests that 5-HT promotes thrombopoiesis from two aspects: one is the direct effect on megakaryocytes. 5-HT could promote the proplatelet formation from megakaryocytes. The second is the indirect effect by promoting the production of TPO, which is a paracrine secretion to influence thrombopoiesis. Disclosures No relevant conflicts of interest to declare.

A selective serotonin receptor agonist for weight loss and management of menopausal vasomotor symptoms in overweight midlife women: a pilot study.

Weight gain and vasomotor symptoms (VMS) are common complaints in midlife women going through the menopause transition. A selective serotonin 2C (5-HT2C) receptor agonist, lorcaserin, which was previously approved by the Food and Drug Administration for weight loss, has unreported observational evidence suggesting improvement in VMS with its use. The goal of this pilot study was to evaluate the efficacy of lorcaserin for weight loss and management of VMS in overweight midlife women. This was a 24-week open label pilot study of 20 overweight midlife women, aged 45-60 years, who were experiencing severe VMS. Participants received lorcaserin at the standard dose of 10 mg twice daily for 12 weeks, followed by 12 weeks of observation off the drug. The primary outcomes were changes in weight and subjectively reported VMS. At the end of 12 weeks, mean change in weight was -2.4 kg (90% CI, -3.2 to -1.7, P < 0.001). However, the participants returned to the baseline weight at 24 weeks. Participants also reported significant subjective improvement in VMS, with a mean ± SD change in self-reported hot flash frequency from baseline to week 12 of -5.4 ± 3.9 (decrease of 1.4 standard deviations). There was a rapid increase in the frequency of VMS within 2 weeks of discontinuation of lorcaserin with a tendency to approach the baseline frequency of VMS. In addition to its weight loss-inducing effect, 5-HT2C receptor modulation may have an additional beneficial effect on VMS in midlife women. A treatment option that targets both weight and VMS in midlife women is attractive. : Video Summary:http://links.lww.com/MENO/A622.

Neuropharmacological and antidepressant-like effects of ZY-1408: A novel serotonin/norepinephrine reuptake inhibitor and serotonin receptor 2C antagonist

Depression is a common mental illness and leading cause of disability. Most current antidepressants are associated with significant limitations, and in particular, a delayed onset and low rate of efficacy. Consequently, there remains an ongoing need for antidepressants that are either more effective or better tolerated than existing standards. We previously identified ZY-1408 as a drug with a novel chemical structure and potential anti-depressant-like activity. Specifically, ZY-1408 is a novel serotonin 2C (5-HT2C) receptor antagonist and serotonin/norepinephrine (5-HT/NE) reuptake inhibitor. In this study, we further investigated the antidepressant-like efficacy of ZY-1408 using in vitro and in vivo behavioral tests. ZY-1408 showed 5-HT2C receptor antagonist and 5-HT/NE reuptake inhibitor properties in vitro. Meanwhile, ZY-1408 decreased immobility in vivo in a dose-dependent manner in rats (via the forced-swim test) and mice (via the tail-suspension test). The behavioral test results do not appear to result from stimulation of locomotor activity. In chronically stressed rats, repeated ZY-1408 treatment significantly reversed depressive-like behavior, including reduced sucrose preference, decreased locomotor activity, and prolonged time to begin eating. Furthermore, in vivo microdialysis showed that administration of ZY-1408 significantly increased extracellular concentrations of 5-HT and NE in the hippocampus of freely moving rats. Thus, ZY-1408 is a potent and orally active 5-HT2C receptor antagonist and 5-HT/NE reuptake inhibitor with antidepressant-like activity in rodents.

The Chronic Treatment With 5-HT2A Receptor Agonists Affects the Behavior and the BDNF System in Mice.

Serotonin 5-HT2A receptors and the brain-derived neurotrophic factor (BDNF) are involved in the pathophysiology and treatment of many psychiatric diseases. However, the interaction between 5-HT2A and BDNF is still poorly understood. In the present paper, the effects of chronic treatment with mixed 5-HT2A/2C receptor agonist DOI, highly selective 5-HT2A agonists TCB-2 and 25CN-NBOH on behavior and the BDNF system have been investigated. Chronic treatment of males of C57Bl/6 mice with DOI, TCB-2 and 25CN-NBOH (1 mg/kg, i.p., 14 days) resulted in desensitization of 5-HT2A receptors. Treatment with 25CN-NBOH significantly increased startle amplitude. At the same time all used drugs failed to affect anxiety, exploratory and stereotyped behavior as well as spatial memory and learning. TCB-2 and 25CN-NBOH increased the BDNF mRNA level. All 5-HT2A agonists increased the proBDNF level but failed to alter the mature BDNF protein level. TrkB and p75NTR mRNA levels were affected by all utilized agonists. All drugs decreased the total level as well as membrane TrkB protein one indicating downregulation of TrkB receptors. All agonists decreased the membrane p75NTR protein level. Thus, we have shown for the first time that the chronic activation of the 5-HT2A receptor with agonists has affected the BDNF system almost on all levels-transcription, proBDNF production, TrkB and p75NTR receptors' level. The obtained data suggested possible suppression in BDNF-TrkB signaling under chronic treatment with 5-HT2A agonists.

Reassessment of the involvement of Snord115 in the serotonin 2c receptor pathway in a genetically relevant mouse model.

SNORD115 has been proposed to promote the activity of serotonin (HTR2C) receptor via its ability to base pair with its pre-mRNA and regulate alternative RNA splicing and/or A-to-I RNA editing. Because SNORD115 genes are deleted in most patients with the Prader-Willi syndrome (PWS), diminished HTR2C receptor activity could contribute to the impaired emotional response and/or compulsive overeating characteristic of this disease. In order to test this appealing but never demonstrated hypothesis in vivo, we created a CRISPR/Cas9-mediated Snord115 knockout mouse. Surprisingly, we uncovered only modest region-specific alterations in Htr2c RNA editing profiles, while Htr2c alternative RNA splicing was unchanged. These subtle changes, whose functional relevance remains uncertain, were not accompanied by any discernible defects in anxio-depressive-like phenotypes. Energy balance and eating behavior were also normal, even after exposure to high-fat diet. Our study raises questions concerning the physiological role of SNORD115, notably its involvement in behavioural disturbance associated with PWS.

Re-assessment of the involvement of Snord115 in the serotonin 2C receptor pathway in a genetically relevant mouse model

SNORD115 has been proposed to promote the activity of serotonin (HTR2C) receptor via its ability to base-pair with its pre-mRNA and regulate alternative RNA splicing and/or A-to-I RNA editing. Because SNORD115 genes are deleted in most patients with the Prader-Willi syndrome (PWS), diminished HTR2C receptor activity could contribute to the impaired emotional response and/or compulsive overeating characteristic of this disease. In order to test this appealing but never demonstrated hypothesis in vivo, we created a CRISPR/Cas9-mediated Snord115 knockout mouse. Surprisingly, we uncovered only modest region-specific alterations in Htr2c RNA editing profiles while Htr2c alternative RNA splicing was unchanged. These subtle changes, whose functional relevance remains uncertain, were not accompanied by any discernible defects in anxio-depressive-like phenotypes. Energy balance and eating behaviour were also normal, even after exposure to high fat diet. Our study raises questions concerning the physiological role of SNORD115, notably its involvement in behavioural disturbance associated with PWS.

Early ethanol pre-exposure alters breathing patterns by disruptions in the central respiratory network and serotonergic balance in neonate rats

Early ethanol exposure alters neonatal breathing plasticity. Respiratory EtOH's effects are attributed to central respiratory network disruptions, particularly in the medullary serotonin (5HT) system. In this study we evaluated the effects of neonatal pre-exposure to low/moderate doses upon breathing rates, activation patterns of brainstem’s nuclei and expression of 5HT 2A and 2C receptors. At PD9, breathing frequencies, tidal volumes and apneas were examined in pups pre-exposed to vehicle or ethanol (2.0 g/kg) at PDs 3, 5 and 7. This developmental stage is equivalent to the 3rd human gestational trimester, characterized by increased levels of synaptogenesis. Pups were tested under sobriety or under the state of ethanol intoxication and when subjected to normoxia or hypoxia. Number of c-Fos and 5HT immunolabelled cells and relative mRNA expression of 5HT 2A and 2C receptors were quantified in the brainstem. Under normoxia, ethanol pre-exposed pups exhibited breathing depressions and a high number of apneas. An opposite phenomenon was found in ethanol pre-treated pups tested under hypoxia where an exacerbated hypoxic ventilatory response (HVR) was observed. The breathing depression was associated with an increase in the neural activation levels of the raphe obscurus (ROb) and a high mRNA expression of the 5HT 2A receptor in the brainstem while desactivation of the ROb and high activation levels in the solitary tract nucleus and area postrema were associated to the exacerbated HVR. In summary, early ethanol experience induces respiratory disruptions indicative of sensitization processes. Neuroadaptive changes in central respiratory areas under consideration appear to be strongly associated with changes in their respiratory plasticity.

Multiscale neurobiological correlates of human neuroticism.

Neuroticism is a heritable personality trait associated with negative emotionality; however, we know little regarding the association between the microscale and macroscale neurobiological substrates of human neuroticism. Cross‐scale correlation analysis may provide such information. In this study, voxel‐wise neuroimaging–neuroticism correlation analyses consistently showed a positive correlation between neuroticism and functional connectivity density (FCD) in the ventral striatum in 274 young Chinese adults. Partial least squares regression analysis showed that the FCD‐neuroticism correlation map was significantly spatially correlated with gene expression profiles in each of six donated human brains. Neuroticism‐related genes derived from the six donors consistently showed significant enrichment in the chemical synaptic transmission, circadian entrainment, long‐term potentiation, inflammatory mediator regulation of transient receptor potential channels, and amphetamine addiction pathways. The protein–protein interaction analysis revealed four hub genes involved in the above pathways, including G protein subunit gamma 10, 5‐hydroxytryptamine receptor 2C, prodynorphin, and calcium/calmodulin‐dependent protein kinase II alpha. By combining multiscale correlation analyses and functional annotations, this study advances our understanding of the genetic and neural substrates of human neuroticism and emphasizes the importance of striatal functional properties in human neuroticism.

The role of blocking serotonin 2C receptor by fluoxetine in the treatment of bulimia

Fluoxetine serves as a primary drug for the pharmacological treatment of binge eating. Its activity usually consists in blocking 2C serotonin receptors. This may be considered to be controversial since agonists of this receptor are effective in pharmacological treatment of bulimia. Bulimia episodes occur as a result of a decrease in serotonergic activity in the central nervous system. The mechanism is clinically confirmed. Drugs which increase the activity of the serotonin system in suppressing binge eating proved effective. The anorexigenic effect of drugs which increase the activity of the serotonin system results from the stimulation of serotonin receptors and not from their blocking. Appetite regulation and binge eating are associated with the activity of the dopaminergic and serotonergic systems. Experimental studies conducted so far prove that the increase in dopaminergic activity in the structures of the reward system is caused by stimulation, and not blocking, of serotonin 2C receptors. The anorexigenic effect of proserotonin drugs may also result from the stimulation of type 3 serotonin receptors and possibly 2C on neurons located in the nucleus of solitary tract. The psychopharmacological investigation conducted in this paper revealed the role of 5-HT2C receptors in the pathogenesis of bulimia nervosa and the mechanism of action of fluoxetine in the treatment of binge eating. Based on existing knowledge, the fact that fluoxetine blocks these receptors does not appear to play a significant role in appetite suppression. Due to few experimental works, the problem requires further research.

A Novel Synthetic Interfering Peptide Tat-3L4F Attenuates Olanzapine-Induced Weight Gain Through Disrupting Crosstalk Between Serotonin Receptor 2C and Protein Phosphatase and Tensin Homolog in Rats.

BackgroundAccompanied with profound efficacy, atypical antipsychotics (AAPs) contribute to metabolic adverse effects with few effective strategies to attenuate. Serotonin 5-HT2C receptor (HTR2C) plays a critical role in hyperphagia and weight gain induced by AAPs, and expression of phosphatase tensin homolog (PTEN) in the hypothalamus also affects feeding behavior and weight change. Moreover, PTEN has a physical crosstalk between PTEN and a region in the third intracellular loop (3L4F) of the HTR2C. Tat-3L4F has the property to disrupt crosstalk between PTEN and HTR2C. This is the first study to our knowledge to investigate the effect of Tat-3L4F on olanzapine-induced metabolic abnormalities and PTEN/ phosphatidylinositol 3-kinase/protein kinase B expression in the hypothalamus in rats.MethodsThe effects of Tat-3L4F were investigated through measuring body weight, food intake, and blood glucose. In addition, PTEN/phosphatidylinositol 3-kinase/protein kinase B level in the hypothalamus was detected by immunofluorescence assay and western blot. Metabolites in the liver tissue were detected by liquid chromatography-mass spectrometry and analyzed by multivariate analyses and pairwise comparison.ResultsOur results showed that hyperphagia and weight gain were evident in the olanzapine alone–fed rats but was attenuated after Tat-3L4F treatment. In addition, oral glucose tolerance test indicated blood glucose at 120 minutes was higher in the olanzapine alone–treated group than in groups treated with vehicle and olanzapine + Tat-3L4F (10 μmol kg−1 per day). Furthermore, compared with olanzapine alone treatment, treatment with Tat-3L4F (10 μmol kg−1 per day) significantly inhibited PTEN expression in the hypothalamus. The olanzapine alone–treated group had the highest bile acid level, followed by the olanzapine with Tat-3L4F (1 μmol kg−1) group, olanzapine with Tat-3L4F (10 μmol kg−1) group, and vehicle group.ConclusionsOur present results reveal that Tat-3L4F is a potential pharmacological strategy for suppressing hyperphagia and weight gain induced by olanzapine, which acts through disrupting crosstalk between HTR2C and PTEN as a result of PTEN downregulation in the hypothalamus.

Association of serotonin 2c receptor gene polymorphism with depression and quality of life indicators in patients before coronary artery bypass grafting

The aim was to study the association of the rs6318 polymorphism of the HTR2C gene with the level of depression and quality of life in patients undergoing coronary artery bypass grafting (CABG). Materials and methods. A total of 116 patients with coronary artery disease (CAD) (age 60 [57; 65] years) were examined before CABG. Depression was assessed in all patients in the preoperative period using the Beck Depression Inventory (BDI). In addition, the quality of life was measured in all patients using the SF-36 questionnaire. Blood samples were collected for the subsequent polymerase chain reaction-based genotyping to detect the rs6318 polymorphism of the HTR2C gene. Statistical analysis was performed using the STATISTICA 10.0 software package (StatSoft Inc., USA). The value of p &lt; 0.05 was considered statistically significant. Results. No significant differences were found in the associations between different genotypes of the HTR2C gene and depression levels. However, certain trends have been established ( p = 0.1). Thus, the pairwise comparison of different genotypes reported that carriers of the CC genotype had higher BDI scores (12 [8; 19]), whereas carriers of the CG genotype ( p = 0.07) and GG genotype ( p = 0.08) had lower BDI scores (3.5 [2; 5] and 8 [0; 25], respectively). The quality of life among carriers of the CC, CG and GG genotypes did not differ significantly. Nevertheless, the median values of almost all indicators (GH, PF, RE, VT) were lower in carriers of the CC genotype. Carriers of the CC genotype suffered more from pain limiting their daily activities than carriers of the GG genotype ( p = 0.04). Homozygous C allele carriers demonstrated poorer mental health than heterozygous carriers (56 [40; 64] vs 82 [72; 92], p = 0.04). Conclusions. Reliable associations of different genotypes of the rs6318 polymorphism of the HTR2C gene with the quality of life parameters have been found in patients with coronary artery disease.

Antidepressant-like effect of a selenopropargylic benzamide in mice: involvement of the serotonergic system.

Major depressive disorder is a psychiatric disorder that requires considerable attention, since it dramatically impairs the quality of life of the sufferers. The available treatments do not have the efficacy needed, often presenting several side effects. Organoselenium compounds and benzamides have presented some pharmacological properties, among them an antidepressant-like effect. This study evaluated the antidepressant-like effect of N-(3-(phenylselanyl)prop-2-yn-1-yl)benzamide (SePB), an organoselenium compound containing a benzamide moiety, on the forced swimming test (FST) and the tail suspension test (TST) in mice, as well as the involvement of the serotonergic system in its effect. SePB, tested after different times (15-120min) and doses (1-50mg/kg, intragastrically (i.g.)), reduced immobility of male mice during FST and TST, without changing locomotor activity in the open-field test (OFT), demonstrating its antidepressant-like effect. SePB (10mg/kg) also produced an antidepressant-like effect in female mice in the TST. The preadministration of the serotonin (5-HT) depletor p-chlorophenylalanine (pCPA; 100mg/kg, intraperitoneal route (i.p.) once daily for 4days) prevented the anti-immobility effect of SePB, indicating that the serotonergic system is involved in the SePB antidepressant-like effect. The preadministration of the selective serotonergic receptor antagonists WAY100635 (0.1mg/kg, subcutaneous route (s.c.), a selective 5-HT1A receptor antagonist), ketanserin (1mg/kg, i.p., a 5-HT2A/2C receptor antagonist), and ondansetron (1mg/kg, i.p., a selective 5-HT3 receptor antagonist) also prevented the anti-immobility effect of SePB, demonstrating that these receptors are involved in the antidepressant-like effect of SePB. The search for new antidepressants drugs is a noteworthy goal. This study has described a new compound with an antidepressant-like effect, whose mechanism of action is related to modulation of the serotonergic system.

A 5-HT1D -receptor agonist protects Dravet syndrome mice from seizure and early death.

Mutations in the SCN1A gene encoding the Nav1.1 sodium channel cause several forms of epilepsy, the most severe is Dravet syndrome (DS). DS patients are at high risk for sudden death and seizures are often triggered by fever or hyperthermia. To improve understanding of how serotonergic ligands might influence DS in this study, we tested several drugs for their effect on hyperthermia-induced seizure using a mouse model of DS consisting of a heterozygous loss of function of Scn1A. We found that a mixed 5-HT2A/2C receptor agonist had no effect while a mixed 5-HT1B/D receptor agonist had a modest effect reducing the severity of seizures. Hypothesizing selective agonists may be more effective, we tested selective 5-HT1B and 5-HT1D receptor agonists, CP-93129 and GR-46611, respectively. Of these GR-46611 significantly increased the threshold of hyperthermia-induced seizure and lowered seizure severity. Given chronically at 1mgkg-1 day-1 , GR-46611 also significantly improved survival of DS mice. Thus, 5-HT1D -receptors may represent a meaningful target for pharmacotherapy for DS with potential relevance for related forms of epilepsy, particularly those with a known sensory trigger such as heat.

Antihyperalgesic effects of intrathecal perospirone in a rat model of neuropathic pain

The descending serotonergic pathway, from the brainstem to spinal cord, modulates various aspects of pain processing. The spinal 5-hydroxytryptamine (5-HT)1A and 5-HT2A receptors play pivotal roles in pain modulation. Perospirone is a novel atypical antipsychotic that serves as a 5-hydroxytryptamine (5-HT)1A receptor agonist, a 5-HT2A receptor antagonist, and a dopamine D2 receptor antagonist. Little is known about the effect of perospirone on pain transmission. Here, we explored whether perospirone attenuated neuropathic and inflammatory pain in the spinal cord. A chronic constriction injury to the sciatic nerve was induced in male Sprague-Dawley rats. We evaluated the effects of intrathecal administration of perospirone (10, 20, or 40 μg) on mechanical and cold hyperalgesia using the electronic von Frey and cold plate tests, respectively. Normal rats were assessed in terms of inflammatory nociception using the formalin test and for motor coordination employing the rotarod test. To define the mechanism underlying the action of perospirone, the effects of intrathecal pretreatment with the 5-HT1A receptor antagonist WAY-100635, the 5-HT2A/2C receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-aminopropane (DOI), and the dopamine D2 receptor agonist sumanirole on perospirone action were examined using the electronic von Frey test and cold plate test. Perospirone dose-dependently alleviated mechanical and cold hyperalgesia, but not inflammatory nociception in the spinal cord, and affected motor coordination. WAY-100635 reversed the antihyperalgesic action of perospirone significantly, but neither DOI nor sumanirole exhibited such an effect. We conclude that perospirone attenuates mechanical and cold hyperalgesia principally via 5-HT1A receptor activation in the spinal cord, and the agent is a promising novel candidate for neuropathic pain relief.

140-OR: Inhibition of Serotonin 2c Receptor Internalization Potentiates Lorcaserin Effect on Body Weight Loss

As a body weight management medicine, lorcaserin, a selective agonist of serotonin 2C receptor (5-HT2CR) which is a G protein-coupled receptor, fails to maintain its effect on body weight loss after a long term administration. Thus, it is necessary to find a way to strengthen its effect on obesity treatment. It has been reported that the effect of lorcaserin on body weight loss is by activating Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus (ARH). However, how POMCARH neuron activity changes after long term lorcaserin treatment remains unknown. In the present study, we found that POMCARH neurons cannot maintain its sensitivity to further lorcaserin stimulation after a long term lorcaserin treatment. By using in vitro electrophysiology recording and c-Fos immunostaining in the brain slice from control mice, we found that acute lorcaserin application significantly increased POMCARH neuron activity. However, this activation effect significantly decreased in mice with lorcaserin administration for consecutive 20 days. By in vivo fiber photometry calcium recording, we found that lorcaserin significantly increased POMCARH neuron activity in vivo at first day, but this activation effect decreased after 10 days lorcaserin treatment and almost disappeared after 20 days lorcaserin treatment. We further showed that this desensitization of POMCARH neurons to lorcaserin stimulation is mainly due to a beta-arrestin-mediated excessive internalization of 5-HT2C receptor in POMCARH neurons. Barbadin, a novel selective β-arrestin/adaptor protein 2 interaction inhibitor, maintains POMCARH neuron sensitivity to further lorcaserin stimulation by blocking prolonged lorcaserin-induced aberrant 5-HT2C receptor internalization. Co-treatment with barbadin also prolongs lorcaserin’s effect on body weight loss and food intake reduction in mice. Overall, our results may provide a potential strategy for facilitating obesity treatment by lorcaserin. Disclosure Y. He: None. H. Liu: None. Y. Xu: None.

Brainstem expression of SLC6A4, HTR2C, NGF, BDNF, TRKANGF, TRKBBDNF and P75NTR following paternal alcohol exposure in the male mouse

We previously showed in the mouse that paternal preconception alcohol exposure (PPAE) affects alcohol sensitivity by analyzing postnatal alcohol preference in the offspring. In this mouse study by using the same animals of the previous investigation we aimed at examining whether or not PPAE may disrupt the epigenetic regulation of postnatal alcohol sensitivity in the offspring by investigating pathways regulating mood, emotion, serotonergic tone and neurotrophins such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). We analyzed the brainstem gene expression of serotonin transporter Solute Carrier Family 6 Member4 (SLC6A4), 5-Hydroxytryptamine Receptor 2C (HTR2C) binding the neurotransmitter serotonin, and NGF, BDNF and their tropomyosin receptor kinase A (TrkANGF) and B (TrKBBDNF) (high-affinity NGF and BDNF receptors) and p75NTR (low-affinity, pan-neurotrophins receptor) in adult offspring that underwent or not postnatal alcohol exposure. We found SLC6A4 elevation and decreased HTR2C in the offspring of chronic alcohol-exposed sires. We also disclosed p75NTR elevation in the offspring of chronically exposed sires as well as postnatal sensitization to low alcohol doses in the offspring of chronically exposed sires for both TrKBBDNF and BDNF. In our PPAE mouse model, where genotype effects can be carefully measured, we observed that the sires’ exposure to alcohol before mating might disrupt the sensitivity to the serotonergic/neurotrophic-associated effects of alcohol influencing the postnatal alcohol preference in the offspring.

FDA Requests Withdrawal of Weight-Loss Drug From Market.

The Food and Drug Administration has requested that the manufacturer of lorcaserin (Belviq, Belviq XR), a serotonin 2C receptor agonist used as an adjunct to diet and exercise for weight loss, voluntarily withdraw the drug from the U.S. market because of an increased occurrence of cancer.