5-HT2 Agonist Research Articles

Serotonin disrupts esophageal mucosal integrity: an investigation using a stratified squamous epithelial model.

Serotonin regulates gastrointestinal function, and mast cells are a potential nonneuronal source of serotonin in the esophagus. Tight junction (TJ) proteins in the esophageal epithelium contribute to the barrier function, and the serotonin signaling pathway may contribute to epithelial leakage in gastroesophageal reflux disease. Therefore, the aim of this study was to investigate the role of serotonin on barrier function, TJ proteins, and related signaling pathways. Normal primary human esophageal epithelial cells were cultured with use of an air-liquid interface system. Serotonin was added to the basolateral compartment, and transepithelial electrical resistance (TEER) was measured. The expression of TJ proteins and serotonin receptor 7 (5-HT7) was assessed by Western blotting. The involvement of 5-HT7 was assessed with use of an antagonist and an agonist. The underlying cellular signaling pathways were examined with use of specific blockers. Serotonin decreased TEER and reduced the expression of TJ proteins ZO-1, occludin, and claudin1, but not claudin4. A 5-HT7 antagonist blocked the serotonin-induced decrease in TEER, and a 5-HT7 agonist decreased TEER. Inhibition of p38 mitogen-activated protein kinase (MAPK) reduced the serotonin-induced decrease in TEER. Inhibition of p38 MAPK blocked the decrease of ZO-1 levels, whereas extracellular-signal-regulated kinase (ERK) inhibition blocked the decrease in occludin levels. Cell signaling pathway inhibitors had no effect on serotonin-induced alterations in claudin1 and claudin4 levels. Serotonin induced phosphorylation of p38 MAPK and ERK, and a 5-HT7 antagonist partially blocked serotonin-induced phosphorylation of p38 MAPK but not that of ERK. Serotonin disrupted esophageal squamous epithelial barrier function by modulating the levels of TJ proteins. Serotonin signaling pathways may mediate the pathogenesis of gastroesophageal reflux disease.

Opioid adjuvant strategy: improving opioid effectiveness.

Opioid analgesics continue to be the mainstay of pharmacologic treatment of moderate to severe pain. Many patients, particularly those suffering from chronic pain, require chronic high-dose analgesic therapy. Achieving clinical efficacy and tolerability of such treatment regimens is hampered by the appearance of opioid-induced side effects such as tolerance, hyperalgesia and withdrawal syndrome. Among the therapeutic options to improve the opioid effectiveness, this current review focuses on strategies combining opioids to other drugs that can modulate opioid-mediated effects. We will discuss about experimental evidences reported for several potential opioid adjuvants, including N-methyl-D-aspartate receptor antagonists, 5-HT7 agonists, sigma-1 antagonists, I2-R ligands, cholecystokinin antagonists, neuropeptide FF-R antagonists and toll-like receptor 4 antagonists.

Prucalopride exerts neuroprotection in human enteric neurons.

Serotonin (5-hydroxytryptamine, 5-HT) and its transporters and receptors are involved in a wide array of digestive functions. In particular, 5-HT4 receptors are known to mediate intestinal peristalsis and recent data in experimental animals have shown their role in neuronal maintenance and neurogenesis. This study has been designed to test whether prucalopride, a well-known full 5-HT4 agonist, exerts protective effects on neurons, including enteric neurons, exposed to oxidative stress challenge. Sulforhodamine B assay was used to determine the survival of SH-SY5Y cells, human enteric neurospheres, and ex vivo submucosal neurons following H2O2 exposure in the presence or absence of prucalopride (1 nM). Specificity of 5-HT4-mediated neuroprotection was established by experiments performed in the presence of GR113808, a 5-HT4 antagonist. Prucalopride exhibited a significant neuroprotective effect. SH-SY5Y cells pretreated with prucalopride were protected from the injury elicited by H2O2 as shown by increased survival (73.5 ± 0.1% of neuronal survival vs. 33.3 ± 0.1%, respectively; P < 0.0001) and a significant reduction of proapoptotic caspase-3 and caspase-9 activation in all neurons tested. The protective effect of prucalopride was reversed by the specific 5-HT4 antagonist GR113808. Prucalopride promotes a significant neuroprotection against oxidative-mediated proapoptotic mechanisms. Our data pave the way for novel therapeutic implications of full 5-HT4 agonists in gut dysmotility characterized by neuronal degeneration, which go beyond the well-known enterokinetic effect.

Editorial: serotonin and irritable bowel syndrome – reconciling pharmacological effects with basic biology; authors' reply

We thank Professor Quigley for his interest in our recent publication.1, 2 In that study, we investigated plasma concentrations of serotonin and its principal metabolite 5-HIAA for differences between IBS patients and healthy controls.1 Due to the prominent role of serotonin in both gut and brain function, different pharmacological therapies aimed at serotonergic targets, including 5HT3 antagonists, 5HT4 agonists and in particular SSRIs have traditionally been administered for IBS with a high variability in treatment efficacy. The Cochrane review from 2011 reports on a significant effect of SSRIs with regard to global improvement but not abdominal pain.3 In a recent meta-analysis, Ford et al. concluded that the relative risk of remaining symptomatic after therapy for SSRIs vs. placebo was 0.68 (95% CI = 0.51–0.91).4 On the other hand, Xie et al. recently showed that SSRIs have no benefit in alleviating symptoms or improving quality of life in IBS patients.5 The contradicting conclusions are probably based on differences in inclusion criteria and thereby in number of studies included in the meta-analyses. Furthermore, it has to be noted that comparing outcomes of trials in IBS patients remains difficult due to a large variety in the definition of study endpoints, as we have shown in a recent systematic review.6 In addition, it remains controversial whether a benefit from SSRI treatment arises from the treatment of co-existent psychopathologies,7 as Ladabaum et al. found no effect of citalopram in nondepressed IBS patients.8 The discrepancy in the evidence for efficacy of SSRIs could also be explained by the heterogeneity of the IBS population. Probably a more selective subgroup for serotonin-targeted therapy could be the solution. Patients could be selected based on psychological comorbidity,8, 9 but pre-treatment assessment of plasma and/or mucosal serotonin metabolism may aid patient selection in the future.1, 10 In this respect, measurement of plasma 5-HIAA appears attractive, as 5-HIAA is less sensitive to oxidative breakdown, compared with 5-HT, and therefore can be measured more reliably. It should however be noted that mere plasma measurements are probably unable to reflect the complexity of serotonergic biology in the gut and brain. Furthermore, Professor Quigley acknowledges the interesting differences in 5-HIAA concentrations between IBS-subtypes, particularly with respect to distinct low 5-HIAA concentrations in the IBS-M subtype in our study.1, 2 He also suggests that the shift of subtypes observed in IBS patients in longitudinal studies would speak against the hypothesis for a role of altered serotonin metabolism in IBS-M.2 Indeed about 50% of IBS patients tend to shift from one subtype to the other, mostly from IBS-M to IBS-D or IBS-C, or vice versa.11 However, this may not contradict our hypothesis. Serotonin is found to affect both gut motility and secretion.12 Therefore, one could speculate that the poorly understood changes in bowel pattern over time may be caused by changes in serotonin metabolism, reflected by plasma 5-HIAA concentrations. A study with a longitudinal design is needed to correlate plasma 5-HIAA concentrations with bowel pattern over time in IBS patients. Declaration of personal and funding interests: None.

Chronic 5-HT4 receptor agonist treatment restores learning and memory deficits in a neuroendocrine mouse model of anxiety/depression

Cognitive disturbances are often reported as serious invalidating symptoms in patients suffering from major depression disorders (MDD) and are not fully corrected by classical monoaminergic antidepressant drugs. If the role of 5-HT4 receptor agonists as cognitive enhancers is well established in naïve animals or in animal models of cognitive impairment, their cognitive effects in the context of stress need to be examined. Using a mouse model of anxiety/depression (CORT model), we reported that a chronic 5-HT4 agonist treatment (RS67333, 1.5mg/kg/day) restored chronic corticosterone-induced cognitive deficits, including episodic-like, associative and spatial learning and memory impairments. On the contrary, a chronic monoaminergic antidepressant drug treatment with fluoxetine (18mg/kg/day) only partially restored spatial learning and memory deficits and had no effect in the associative/contextual task. These results suggest differential mechanisms underlying cognitive effects of these drugs. Finally, the present study highlights 5-HT4 receptor stimulation as a promising therapeutic mechanism to alleviate cognitive symptoms related to MDD.

CGRP and migraine.

Migraine has been estimated to be the seventh highest cause of disability worldwide, and the third most common disease worldwide after dental caries and tension type headache. However, the use of currently available acute and prophylactic medications to control this condition, such as 5-HT1 agonists (triptans) and beta-blockers, is limited by side effects and efficacy so that alternative and more specific treatments are required. More recently, an improved understanding of the pathophysiology of disease has allowed investigation of new therapeutic targets. The 37 amino acid neuropeptide calcitonin gene-related peptide (CGRP) has been shown to play a crucial role in the trigeminocervical complex pathway for nociception in the head. Studies have demonstrated elevated levels in the external jugular vein during the headache phase of migraine, with reduction following headache resolution. Furthermore, CGRP infusion triggers migraine type headache and subsequent treatment with triptans results in normalization of CGRP levels. This neuropeptide is therefore thought to have a central role in pain modulation as it participates in the neurovascular pathway and contributes to the vasodilation and neurogenic inflammation, which leads to migrainous attacks. Targeting CGRP may provide the ideal therapeutic tool needed for control of this common and debilitating illness. The three studies chosen for this month’s journal club are a small sample of the large amount of research being performed on CGRP. The first investigates whether its measurement can be used to classify migraine. The second and third articles are phase II clinical trials which investigate the use of CGRP antagonists and a monoclonal antibody CGRP

Managing opioid-induced constipation.

in depth. Nursing professionals are critical for identifying constipation in patients using opioids and ensuring that these simple measures to alleviate distress and improve quality of life are implemented effectively. Where simple laxatives are insufficient to relieve OIC, a newer, more-expensive laxative approved for treating chronic constipation (i.e., lubiprostone or prucalopride) or an opioid antagonist should be considered. Lubiprostone stimulates intestinal fluid and electrolyte secretion by activating type 2 chloride channels. While lubiprostone is approved for treating refractory constipation in the USA and EU, it is only licensed for treating OIC in noncancer pain in the former. Prucalopride, a selective 5-HT4 agonist, is approved for treating refractory constipation in the UK, but not in the USA. These agents are modestly effective in treating OIC associated with non-cancer pain. The endpoints varied across studies precluding a comparison of their efficacy. Because the studies compared these drugs to placebo, the incremental benefit of these drugs over simple laxatives is unknown. Finally, their efficacy in OIC related to cancer pain is unknown. Of the μ-opioid-receptor antagonists used to treat OIC, some (i.e., naloxegol, methylnaltrexone) have peripheral effects only. Others (i.e., naloxone) also have central effects. The central effects may predispose to opioid withdrawal and reduce analgesia in some patients. Naloxegol comprises naloxone conjugated with polyethylene glycol, reducing its ability to cross the blood–brain barrier. Compared with placebo, the number needed to treat (NNT) for treating OIC with oral naloxegol (25 mg) in adults with chronic noncancer pain is approximately 7. In the USA, the approved indication for naloxegol use is OIC in non-cancer pain. In the EU, the approved indication is OIC in adult patients who have had an inadequate response to laxatives. In contrast to naloxegol, methylnaltrexone, is available only as a subcutaneous injection, and is essentially approved for treating OIC in patients with chronic non-cancer pain or advanced illness receiving palliative care in the USA and EU. In the pivotal study (Thomas et al, 2008) conducted in patients with an advanced illness (60% had cancer), 48% treated with a single dose of methylnaltrexone (0.15 mg/kg) versus 15% of placebo-treated U p to one third of the population in the western world report chronic pain. Pain causes distress and disability and has adverse socioeconomic consequences. Opioids are effective and have a favourable risk–benefit profile in conditions associated with acute pain or end-of-life pain. However, the widespread use of opioids, particularly newer semi-synthetic and synthetic opioids, for chronic non-cancer pain, has fuelled a crisis of iatrogenic opioid abuse, addiction, side effects, overdoses, and deaths, with no demonstrable reduction in the burden of chronic pain (Ballantyne and Sullivan, 2015). In the context of these opioid prescribing patterns, opioid-induced constipation (OIC) is common, does not decrease over time, compromises patient satisfaction with analgesic treatment, and limits opioid use (Camilleri et al, 2014). In a population-based survey (Cook et al, 2008), 57% of individuals with chronic non-cancer pain using opioids experienced constipation that they associated with opioid treatment. Moreover, 33% reported constipation as their most bothersome symptom. It is therefore crucial to ask patients on opioids about their bowel habits—not only stool frequency, but also other symptoms of constipation—and elicit changes in bowel patterns. When dealing with OIC, it is prudent to assess whether it is appropriate to use opioids to manage pain, and to discontinue them if not. The long-term use of opioids in patients with non-cancer non-palliative pain (e.g. chronic abdominal pain, fibromyalgia) should be strongly discouraged. Alternatives to opioids —nonopioid analgesics, antidepressant or antiepileptic medications in patients with neuropathic pain, and non-pharmacological adjuncts (e.g. meditation, cognitive behavioural therapy, and neurostimulators)—should be considered. If opioids are essential, anecdotal experience

Hypoxic Stress-Induced Serotonergic Stimulation Controls Hematopoietic Stem Cell Production Via the Hypothalamic-Pituitary-Interrenal Axis and Glucocorticoid Signaling

There is increasing evidence that neuronal signals contribute to adult hematopoietic stem cell (HSC) production and maintenance; however, the mechanisms by which the central nervous system regulates HSCs and/or the HSC niche and its functional necessity during vertebrate HSC development remains unclear. Serotonin (5HT), a neurotransmitter in the brain and a hormone peripherally, was identified in a screen for HSC modulators in zebrafish. Exposure to 5HT or fluoxetine (5HT reuptake inhibitor) increased hematopoietic stem and progenitor cell (HSPC) formation in the zebrafish aorta-gonad-mesonephros (AGM) region as shown by runx1/cmyb in situ hybridization, and confirmed by FACS and qRT-PCR analysis (p<0.05). The stimulatory effect of 5HT was seen both during HSPC niche formation, as well as when AGM HSPCs emerge and expand. Peripheral and neuronal 5HT are synthesized by tryptophan hydroxylase 1 (TPH1) and TPH2, respectively. Chemical inhibition of these rate-limiting enzymes decreased HSC numbers during HSPC emergence (36 hpf). Using morpholino-mediated knockdown, only the effects of selective tph2 reduction on HSCs, and not that of tph1, were found to persist by 48 hpf (p<0.05), which could be rescued by exogenous 5HT; this finding was confirmed using an inducible tph2 -ablation model. Although the sympathetic nervous system (SNS) can contribute to HSC emergence, the effect of 5HT was independent of SNS function as shown using 6-hydroxydopamine (6-OHDA) to induce sympathetic nerve lesions. 5HT can activate the hypothalamic-pituitary-adrenal (HPA) axis, leading to cortisol production and activation of glucocorticoid receptor (GR) to mediate peripheral responses. Indeed, mRNA levels of corticotropin-releasing hormone receptor, pro-opiomelanocortin (pomc) and nr3c1 (GR), as well as cortisol levels were increased in 5HT-treated embryos (p<0.05). In contrast, cortisol production was decreased in tph2 morphants (p<0.05). Consistent with a role for neuronal 5HT in regulating HSCs through the Hypothalamic-Pituitary-Interrenal (HPI) axis (teleost HPA axis counterpart) and peripheral cortisol production, exposure to GR agonists hydrocortisone and dexamethasone increased embryonic HSPC production, while MO-knockdown of GR or analysis of GR mutants revealed drastic reductions in HSPCs and rag2+ lymphoid progenitors. Further, epistasis analysis revealed the impact of 5HT or GR agonist on HSPCs was abrogated upon MO knockdown of GR, whereas GR agonist treatment rescued HSPC numbers in corticotropin-releasing hormone and pomc morphants (p<0.05). The HPA/I axis is well recognized as a "stress response" pathway; we, and others, previously showed that local hypoxia and hypoxic stress-induced Hypoxia Inducible Factor 1a (HIF1a) activity play a pivotal role during embryonic HSPC development. We therefore examined whether hypoxic stimulation can initiate serotonergic and HPI Axis-mediated regulation of HSPC production. Consistent with previous reports, HIF1a activation by cobalt (II) chloride (CoCl2) increased runx1 + HSPCs in the AGM; CoCl2 exposure also elevated tph2 (but not tph1) and HPI axis gene expression and total cortisol production (p<0.05). Furthermore, the effect of CoCl2 stimulation on AGM HSPCs is blocked in tph2 morphants (p<0.05), suggesting that HIF1a activates TPH2-mediated 5HT production to impact HSPC number. Collectively, our data highlight a novel regulatory mechanism controlling embryonic HSPC induction and expansion that exploits the hypoxic stress response to induce serotonergic stimulation of the HPI axis and glucocorticoid signaling. DisclosuresNo relevant conflicts of interest to declare.

Serotonin (5-HT)1A receptor agonism and 5-HT7 receptor antagonism ameliorate the subchronic phencyclidine-induced deficit in executive functioning in mice.

Reversal learning (RL), a type of executive function, dependent on prefrontal cortical function, is impaired in rodents by subchronic (sc) treatment with the N-methyl-D-aspartate receptor antagonist, phencyclidine (PCP), a widely studied model of cognitive impairment in schizophrenia (CIS). The principal objective of this study was to determine the ability of serotonin (5-HT)1A partial agonism and 5-HT7 receptor antagonism to improve RL in scPCP-treated mice. Male C57BL/6J mice were trained on an operant RL (ORL) task, then received PCP, 10mg/kg, or saline, bid, for 7days, followed by a 7-day washout period. scPCP significantly diminished the percent correct responding, increased total incorrect trials, and total incorrect responses, in the reversal phase performance of the ORL task. Pre-treatment with the selective 5-HT1A partial agonist, tandospirone, or the selective 5-HT7 antagonist, SB269970, but not the 5-HT7 agonist, AS 19, reversed the scPCP-induced deficit in RL. Pre-treatment with atypical antipsychotic drug lurasidone, which is a 5-HT1A partial agonist and 5-HT7 antagonist, as well as a 5-HT2A and dopamine (D)2 antagonist, also reversed RL deficit in the scPCP-treated mice. Furthermore, the selective 5-HT1A antagonist, WAY100635, blocked the ability of lurasidone to reverse the scPCP-induced RL deficit. These results indicate that 5-HT7 antagonism and 5-HT1A partial agonism contribute to restoration of RL in scPCP-treated mice. It is suggested that these two mechanisms are effective in restoring RL by decreasing excessive GABAergic inhibition of cortical pyramidal neurons following withdrawal of scPCP treatment.

Behavioral effects of D3 receptor inhibition and 5-HT4 receptor activation on animals undergoing chronic cannabinoid exposure during adolescence.

Chronic exposure to cannabinoids during adolescence results in long-lasting behavioral deficits that match some symptomatologic aspects of schizophrenia. The aim of this study was to investigate the reversibility of the emotional and the cognitive effects of chronic exposure to cannabinoids during adolescence, via subsequent modulation of the serotoninergic 5-HT4 and dopaminergic D3 receptors. RS67333 as a 5-HT4 agonist and U-99194A as a D3 antagonist were administered separately at 1 mg/kg and 20 mg/kg, and in combination at 0.5 mg/kg and 10 mg/kg to adult animals undergoing chronic treatment with the synthetic cannabinoid receptor agonist WIN55,212-2 (1 mg/kg) during adolescence. Animals were tested for anxiety-like behavior and episodic-like memory in the open field and novel object recognition tests respectively 30 minutes after the last drug administration. Chronic WIN55,212-2 treated animals exhibited a lasting disruption of episodic memory and increased anxiety levels. The effect on episodic-like memory were partially restored by acute administration of RS67333 and U-99194A and completely by administration of both drugs in combination at lower doses. However, only RS67333 (20 mg/kg) improved the anxiogenic-like effect of WIN55,212-2. These findings give further support that chronic exposure to cannabinoids during adolescence may be used as an animal model for schizophrenia, and highlight D3 and 5-HT4 receptors as potential targets for an enhanced treatment of the cognitive aspect of this disease.

A National Survey and Needs Assessment on Choices of Therapeutic Agents for Chronic Idiopathic Constipation and Constipation Predominant Irritable Bowel Syndrome: A Canadian Perspective

Introduction: Chronic Idiopathic Constipation (CIC) and constipation-predominant Irritable Bowel Syndrome (IBS-C) are common functional lower gastrointestinal disorders that impair patients' quality of life; despite this, therapies remain unsatisfactory to patients and treating physicians. In 2014, ACG and AGA published two clinical guidelines independently. In a national survey, we aim to evaluate: 1. Canadian gastroenterologists (GIs) practice patterns in the utilization of therapeutic agents listed in the two guidelines; 2. GIs satisfaction with these agents for their CIC and IBS-C patients; and 3. the usefulness of these new guidelines in their clinical practice. Methods: In February 2015, a 9-item questionnaire was sent to 350 Canadian GIs (Converge, Toronto, ON, Canada) to determine their practice demographic information and practice approaches to CIC and IBS-C management including stool softener, fibre supplement, stimulant and osmotic laxative, 5-HT4 agonist and guanylate cyclase-C (GCC) agonist therapies. The study closed in May 2015. Results: The response rate to the survey was 15% (n=52). Almost all (96%) responders follow a standard, stepwise approach for managing patients with CIC and IBS-C. However, they believe that only 23% of referring physicians follow the same approach. Reported first-line therapy (osmotic laxatives) was similar for IBS-C and CIC but second-line therapy differed for CIC (bulking agents) and IBS-C (GCC agonist). Nearly 80% of responders indicated that GCC agonists were the most satisfactory therapy for IBS-C and CIC; despite this, 61% of responders and 64% of referring physicians (reported by the responders) are reluctant to move from over-the-counter to prescription agents. Among the 68% of responders who are aware of the 2 published guidelines, only 51% found the guidelines helpful in prioritizing treatment choices, and 69% of responders indicated that a treatment algorithm, applicable to Canadian practice, would be valuable. Conclusion: This survey demonstrates a need for an education program to standardize and enhance the treatment of CIC and IBS-C. The majority of Canadian GIs would welcome a practical management algorithm to translate new published guidelines and the role of new therapeutic agents into clinical practice. Based on this needs assessment, a comprehensive treatment algorithm has been developed and will be evaluated for the management of IBS-C and CIC in Canadian practice.

Reduced vesicular monoamine transport disrupts serotonin signaling but does not cause serotonergic degeneration

We previously demonstrated that mice with reduced expression of the vesicular monoamine transporter 2 (VMAT2 LO) undergo age-related degeneration of the catecholamine-producing neurons of the substantia nigra pars compacta and locus ceruleus and exhibit motor disturbances and depressive-like behavior. In this work, we investigated the effects of reduced vesicular transport on the function and viability of serotonin neurons in these mice. Adult (4–6months of age), VMAT2 LO mice exhibit dramatically reduced (90%) serotonin release capacity, as measured by fast scan cyclic voltammetry. We observed changes in serotonin receptor responsivity in in vivo pharmacological assays. Aged (months) VMAT2 LO mice exhibited abolished 5-HT1A autoreceptor sensitivity, as determined by 8-OH-DPAT (0.1mg/kg) induction of hypothermia. When challenged with the 5HT2 agonist, 2,5-dimethoxy-4-iodoamphetamine (1mg/kg), VMAT2 LO mice exhibited a marked increase (50%) in head twitch responses. We observed sparing of serotonergic terminals in aged mice (18–24months) throughout the forebrain by SERT immunohistochemistry and [3H]-paroxetine binding in striatal homogenates of aged VMAT2 LO mice. In contrast to their loss of catecholamine neurons of the substantia nigra and locus ceruleus, aged VMAT2 LO mice do not exhibit a change in the number of serotonergic (TPH2+) neurons within the dorsal raphe, as measured by unbiased stereology at 26–30months. Collectively, these data indicate that reduced vesicular monoamine transport significantly disrupts serotonergic signaling, but does not drive degeneration of serotonin neurons.

5-HT6 receptor agonism facilitates emotional learning.

Serotonin (5-HT) and its receptors play crucial roles in various aspects of mood and cognitive functions. However, the role of specific 5-HT receptors in these processes remains to be better understood. Here, we examined the effects of the selective and potent 5-HT6 agonist (WAY208466) on mood, anxiety and emotional learning in mice. Male C57Bl/6J mice were therefore tested in the forced swim test (FST), elevated plus-maze (EPM), and passive avoidance tests (PA), respectively. In a dose-response experiment, mice were treated intraperitoneally with WAY208466 at 3, 9, or 27 mg/kg and examined in an open field arena open field test (OFT) followed by the FST. 9 mg/kg of WAY208466 reduced immobility in the FST, without impairing the locomotion. Thus, the dose of 9 mg/kg was subsequently used for tests of anxiety and emotional learning. There was no significant effect of WAY208466 in the EPM. In the PA, mice were trained 30 min before the treatment with saline or WAY208466. Two separate sets of animals were used for short term memory (tested 1 h post-training) or long term memory (tested 24 h post-training). WAY208466 improved both short and long term memories, evaluated by the latency to enter the dark compartment, in the PA. The WAY208466-treated animals also showed more grooming and rearing in the light compartment. To better understand the molecular mechanisms and brain regions involved in the facilitation of emotional learning by WAY208466, we studied its effects on signal transduction and immediate early gene expression. WAY208466 increased the levels of phospho-Ser845-GluA1 and phospho-Ser217/221-MEK in the caudate-putamen. Levels of phospho-Thr202/204-Erk1/2 and the ratio mature BDNF/proBDNF were increased in the hippocampus. Moreover, WAY208466 increased c-fos in the hippocampus and Arc expression in both hippocampus and prefrontal cortex (PFC). The results indicate antidepressant efficacy and facilitation of emotional learning by 5-HT6 receptor agonism via mechanisms that promote neuronal plasticity in caudate putamen, hippocampus, and PFC.

Stimulation of 5-HT7 receptor during adolescence determines its persistent upregulation in adult rat forebrain areas

Brain serotonin 7 (5-HT7) receptors play an important functional role in learning and memory, in regulation of mood and motivation, and for circadian rhythms. Recently, we have studied the modulatory effects of a developmental exposure (under subchronic regimen) in rats with LP-211, a brain-penetrant and selective 5-HT7 receptor agonist. We aimed at further deciphering long-term sequelae into adulthood. LP-211 (0.250 mg/kg i.p., once/day) was administered for 5 days during the adolescent phase (postnatal days 43-45 to 47-49). When adult (postnatal days >70), forebrain areas were obtained for ex vivo immunohistochemistry, whose results prompted us to reconsider the brain connectivity maps presented in our previous study (Canese et al., Psycho-Pharmacol 2015;232:75-89.) Significant elevation in levels of 5-HT7 receptors were evidenced due to adolescent LP-211 exposure, in dorsal striatum (which also shows an increase of dopaminergic D2 auto-receptors) and-unexpectedly-in piriform cortex, with no changes in ventral striatum. We observed that functional connectivity from a seed on the right hippocampus was more extended than reported, also including the piriform cortex. As a whole, the cortical loop rearranged by adolescent LP-211 exposure consisted in a hippocampus receiving connections from piriform cortex and dorsal striatum, the latter both directly and through functional control over the 'extended amygdala'. Such results represent a starting point to explore neurophysiology of 5-HT7 receptors. Further investigation is warranted to develop therapies for sleep disorders, for impaired emotional and motivational regulation, for attentive and executive deficit. The 5-HT7 agonist LP-211 (0.250 mg/kg i.p., once/day) was administered for 5 days during adolescence (postnatal days 43-45 to 47-49) in rats. When adult (postnatal days >70), a significant elevation in levels of 5-HT7 receptors were evidenced in dorsal striatum and-unexpectedly-in piriform cortex.

Effect of 5-hydroxytryptamine receptor 4 agonist mosapride on human gastric accommodation.

Impaired gastric accommodation is one of the major features of functional dyspepsia. Mosapride citrate is a 5-hydroxytryptamine receptor 4 (5-HT4) agonist, which is shown to improve upper abdominal symptoms. However, effect of mosapride on gastric accommodation was not clear. We tested the hypothesis that mosapride enhances the gastric accommodation in normal individuals. Fourteen male healthy volunteers completed this study. Single administration of mosapride or placebo was performed randomly with more than 1-week interval. Subjects swallowed a triple-lumen polyvinyl tube with a polyethylene bag. The bag was positioned in the proximal stomach and the minimal distending pressure (MDP) was determined. The ramp distension starting from the MDP was then performed and subjects were instructed to score their perception using ordinate scales. Next the intra-bag pressure was set at MDP + 2mmHg and a liquid meal was administered 30min later, and the intra-bag volume was recorded for 60min. We compared the MDP, perception scores, and the intra-bag volume changes by administering placebo and mosapride. Minimal distending pressure was not significantly different in subjects receiving mosapride or placebo. Treatment with mosapride had no effect on intra-bag pressures or volumes inducing first sensation or discomfort. Gastric accommodation, expressed as the difference between pre- and postmeal intra-bag volumes, and the percent change of the intra-bag volumes by the meal was significantly enhanced by mosapride compared with placebo. This is the first study clearly demonstrating that single administration of 5-HT4 agonist can enhance gastric accommodation in humans. (Umin.ac.jp, number UMIN000014063).

Development and Validation of UV Spectrophotometric Method of Naratriptan Hydrochloride in Bulk and Pharmaceutical Formulatio

NH-Hydrochloride (NH) is a selective 5-HT1 agonist developed for the acute treatment of migraine which acts by stimulating constriction of dilated cranial arteries and by inhibiting the release of neurogenic inflammatory mediators. A simple, sensitive, precise, accurate and economical UV-Spectrophotometric method has been developed for the determination of NH in bulk and pharmaceutical dosage form. Absorption for NH was measured at maximum wavelength 281nm. The percentage recovery of NH in pharmaceutical dosage form was found to be 99.43 to 98.53 %. The developed method was validated with respect to linearity, accuracy (recovery), precision and specificity. Beers law was obeyed in the concentration range of 2-10μg/ml having line equation y = 0.019x with correlation coefficient of 0.99. Results of the analysis were validated according to the ICH guidelines. The results obtained were statistically evaluated and were found to be accurate and reproducible. The proposed method can be successfully applied for the estimation of Naratriptan Hydrochloride in bulk and pharmaceutical dosage form.

Pharmacological agents for the prevention of vestibular migraine.

Vestibular migraine is a common cause of episodic vertigo. Many preventive treatments have been proposed for this condition, including calcium antagonists, beta-blockers, antidepressants, anticonvulsants, selective 5-HT1 agonists, serotonin antagonists and non-steroidal anti-inflammatory drugs (NSAIDs). To assess the effects of pharmacological agents for the prevention of vestibular migraine. The Cochrane Ear, Nose and Throat Disorders Group (CENTDG) Trials Search Co-ordinator searched the CENTDG Trials Register; Central Register of Controlled Trials (CENTRAL 2015, Issue 5); PubMed; EMBASE; CINAHL; Web of Science; Clinicaltrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 5 June 2015. Randomised controlled trials (RCTs) in adults (over 18 years) with a diagnosis of vestibular migraine orprobable vestibular migraine according to the Bárány Society/International Headache Society (IHS) criteria, treated in any setting, comparing pharmacological treatments used in the prevention of vestibular migraine, including beta-blockers, calcium antagonists, anticonvulsants, antidepressants, serotonin antagonists and non-steroidal anti-inflammatory drugs (NSAIDs) against placebo or no treatment. We used the standard methodological procedures expected by The Cochrane Collaboration. Our literature search identified 558 reports, however only 11 were sufficiently relevant for further assessment. We excluded two studies because they did not use the IHS diagnostic criteria for vestibular migraine. We excluded a further eight studies for various reasons related to their design (e.g. lack of placebo or no treatment comparator), aim (e.g. treatment of vestibular migraine rather than prevention) or conduct (e.g. early termination). We identified one ongoing study comparing metoprolol to placebo. The results of this study are awaited; recruitment of the last patient is expected by the end of 2016. We found no evidence from RCTs to answer the question set out in the review objectives. This review has identified the need for well-designed randomised controlled trials to answer questions about the efficacy of current and new treatments.

An Orally Active Phenylaminotetralin-Chemotype Serotonin 5-HT7 and 5-HT1A Receptor Partial Agonist that Corrects Motor Stereotypy in Mouse Models.

Stereotypy (e.g., repetitive hand waving) is a key phenotype of autism spectrum disorder, Fragile X and Rett syndromes, and other neuropsychiatric disorders, and its severity correlates with cognitive and attention deficits. There are no effective treatments, however, for stereotypy. Perturbation of serotonin (5-HT) neurotransmission contributes to stereotypy, suggesting that distinct 5-HT receptors may be pharmacotherapeutic targets to treat stereotypy and related neuropsychiatric symptoms. For example, preclinical studies indicate that 5-HT7 receptor activation corrects deficits in mouse models of Fragile X and Rett syndromes, and clinical trials for autism are underway with buspirone, a 5-HT1A partial agonist with relevant affinity at 5-HT7 receptors. Herein, we report the synthesis, in vitro molecular pharmacology, behavioral pharmacology, and pharmacokinetic parameters in mice after subcutaneous and oral administration of (+)-5-(2'-fluorophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine ((+)-5-FPT), a new, dual partial agonist targeting both 5-HT7 (Ki = 5.8 nM, EC50 = 34 nM) and 5-HT1A (Ki = 22 nM, EC50 = 40 nM) receptors. Three unique, heterogeneous mouse models were used to assess the efficacy of (+)-5-FPT to reduce stereotypy: idiopathic jumping in C58/J mice, repetitive body rotations in C57BL/6J mice treated with the NMDA antagonist, MK-801, and repetitive head twitching in C57BL/6J mice treated with the 5-HT2 agonist, DOI. Systemic (+)-5-FPT potently and efficaciously reduced or eliminated stereotypy in each of the mouse models without altering locomotor behavior on its own, and additional tests showed that (+)-5-FPT, at the highest behaviorally active dose tested, enhanced social interaction and did not cause behaviors indicative of serotonin syndrome. These data suggest that (+)-5-FPT is a promising medication for treating stereotypy in psychiatric disorders.

Design and validation of a homogeneous time-resolved fluorescence cell-based assay targeting the ligand-gated ion channel 5-HT3A

Ligand-gated ion channels (LGICs) are considered as attractive protein targets in the search for new therapeutic agents. Nowadays, this strategy involves the capability to screen large chemical libraries. We present a new Tag-lite ligand binding assay targeting LGICs on living cells. This technology combines the use of suicide enzyme tags fused to channels of interest with homogeneous time-resolved fluorescence (HTRF) as the detection readout. Using the 5-HT3 receptor as system model, we showed that the pharmacology of the HALO-5HT3 receptor was identical to that of the native receptor. After validation of the assay by using 5-HT3 agonists and antagonists of reference, a pilot screen enabled us to identify azelastine, a well-known histamine H1 antagonist, as a potent 5-HT3 antagonist. This interesting result was confirmed with electrophysiological experiments. The method described here is easy to implement and could be applicable for other LGICs, opening new ways for the screening of chemical libraries.

Aggression and anxiety in adolescent AAS-treated hamsters: A role for 5HT3 receptors

Previously, we have shown that anabolic androgenic steroid (AAS) exposure throughout adolescence stimulates offensive aggression while also reducing anxious behaviors during the exposure period. Interestingly, AAS exposure through development correlates with alterations to the serotonin system in regions known to contain 5HT3 receptors that influence the control of both aggression and anxiety. Despite these effects, little is known about whether these separate developmental AAS-induced behavioral alterations occur as a function of a common neuroanatomical locus. To begin to address this question, we localized 5HT3 receptors in regions that have been implicated in aggression and anxiety. To examine the impact these receptors may have on AAS alterations to behavior, we microinjected the 5HT3 agonist mCPBG directly into a region know for its influence over aggressive behavior, the lateral division of the anterior hypothalamus, and recorded alterations to anxious behaviors using the elevated plus maze. AAS exposure primarily reduced the presence of 5HT3 receptors in aggression/anxiety regions. Accordingly, mCPBG blocked the anxiolytic effects of adolescent AAS exposure. These data suggest that the 5HT3 receptor plays a critical role in the circuit modulating developmental AAS-induced changes to both aggressive and anxious behaviors, and further implicates the lateral division of the anterior hypothalamus as an important center for the negative behavioral effects of developmental AAS-exposure.