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YH12852, a novel, highly selective 5‐hydroxytryptamine 4 (5‐HT4) receptor agonist, is currently under development to treat patients with functional constipation. In this study, we aimed to develop a pharmacokinetic (PK)–pharmacodynamic (PD) model that adequately described the time courses of the plasma concentrations of YH12852 and its prokinetic effect as assessed by the Gastric Emptying Breath Test (GEBT) and to predict the prokinetic effect of YH12852 at higher doses through PD simulation. We used the plasma concentrations of YH12852 from patients with functional constipation and healthy subjects and the GEBT results from healthy subjects obtained from a phase I/IIa trial. The PK‐PD modeling and covariate analysis were performed using NONMEM software. The prokinetic effect of YH12852 was described using a semimechanistic multicompartment PD model and an empirical model by Ghoos et al. A two‐compartment model with first‐order absorption adequately described the observed concentration‐time profiles of YH12852. The semimechanistic multicompartment PD model and the revised Ghoos model with two slope parameters adequately described the observed kPCDt (the percent dose of 13C excreted in the exhaled air at minute t after completing the test meal, multiplied by 1000) values. YH12852 accelerated gastric emptying even at low doses of 0.05–0.1 mg, and its prokinetic effect was greater in subjects suffering from more severe functional constipation. The PD simulation experiments revealed that the change from baseline in the half time for gastric emptying induced by YH12852 increased in a dose‐dependent manner at 0.05–5 mg although the results at doses >0.1 mg were extrapolated. We also showed that the empirical Ghoos model is a special case of the general semimechanistic multicompartment PD model for gastric emptying.

Serotonin (5-hydroxytryptamine [5-HT]) synthesized and released in enterochromaffin (EC) cells participates in various functions in the gastrointestinal tract by acting on a diverse range of 5-HT receptors (HTRs) expressed on smooth muscle, enteric neurons, and epithelial cells. We previously observed that genes encoding HTR2A, HTR2B, and HTR4 are expressed in murine intestinal organoids, suggesting the expression of these HTRs in intestinal epithelial cells. The present study investigated the localization of these HTRs in the murine intestine by immunofluorescence staining. HTR2A, HTR2B, and HTR4 localized in individual solitary cells in the epithelium, while HTR2C was observed in the lamina propria. In the epithelium, HTR2A, HTR2B, and HTR4 colocalized with 5-HT, and HTR4 colocalized with glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). Murine intestinal organoids show a colocalization pattern that is similar to in vivo HTR2A and HTR4 with 5-HT, GLP-1, and PYY. Intraperitoneal and intragastric administration of tegaserod, an HTR4 agonist, failed to alter plasma GLP-1 levels in fasted mice. However, intragastric but not intraperitoneal administration of tegaserod reduced dietary lipid-induced increases of plasma GLP-1 levels. This action of tegaserod was inhibited by co-administration of RS39604, an HTR4 antagonist. These results suggest that murine ileal GLP-1/PYY-producing enteroendocrine (EE) cells express HTR4, while 5-HT-producing EC cells express HTR2A, HTR2B, and HTR4. In addition, the observations regarding in vivo GLP-1 secretion suggest that HTR4 signaling in ileal EE cells suppresses dietary lipid-induced GLP-1 secretion. We thus propose that EC and EE cells may interact with each other through paracrine signaling mechanisms.

Background and aim Paralytic ileus is a common intestinal dysfunction in critically ill patients, which results in complications and poor hospital outcomes. There are still no established effective medications, except correcting the primary causes and prokinetics trial, which have limited efficacy and potential adverse events. This study aims to evaluate the efficacy of prucalopride on paralytic ileus in critically ill patients. Methods A randomized, double-blind, placebo-controlled trial of five consecutive days treatment periods was conducted. Critically ill patients with paralytic ileus were included. The primary endpoint was the improvement of bowel dilatation on plain abdominal radiography. The secondary endpoint was the change of abdominal circumference. Results Twenty patients were consecutively enrolled in the study. There was no significant difference in baseline characteristics of patients. The common causes of hospitalization were infection and respiratory problems. The maximum large bowel diameters dramatically decreased in prucalopride group and reached maximum point on the third day after intervention when compared with placebo (-2.1 [± 1.8] vs 0.3 [± 1.5] cm, P = 0.01). The maximum small bowel diameters were noticeably less decreased and were not significantly different when compared with placebo. The abdominal circumferences notably decreased and significantly diverged from placebo on the third day. Conclusions Prucalopride was an effective enterokinetic agent to improve non-severe inflammatory/ischemic bowel conditions related paralytic ileus in critically ill patients. Its effect was predominant on large intestine but could not be well demonstrated on small bowel in this study. Future study or concomitant other prokinetics for upper gut motility should be further evaluated.

Summary Background Agonists of 5‐hydroxytryptamine 4 receptor are potential agents for irritable bowel syndrome with predominant constipation (IBS‐C). However, only tegaserod has been approved for a very limited population in the US. Aim To evaluate the efficacy and safety of minesapride in patients with Rome IV defined IBS‐C. Methods A double‐blind, placebo‐controlled, dose‐finding study was performed. Overall, 411 patients were randomised to receive minesapride at 10, 20 or 40 mg/d, or placebo for 12 weeks. The primary endpoint was Food and Drug Administration (FDA) composite endpoint (responder: a patient who reported an increase in one or more complete spontaneous bowel movements from baseline and improvement of ≥30% from baseline in weekly average of worst abdominal pain score, both in the same week for ≥6/12 weeks). Results The FDA composite responder rate was 13.6% (14/103) in the placebo group, 13.6% (14/103) in the 10 mg group, 19.2% (20/104) in the 20 mg group and 14.9% (15/101) in the 40 mg group, and no dose‐response relationship was found. A greater percentage of minesapride 40 mg‐treated patients than placebo‐treated patients met both responder requirements for ≥9/12 weeks as the stricter composite evaluation (P

We hypothesized that DSP-6952, a partial agonist of the 5-hydroxytryptamine type-4 receptor and a gastrointestinal prokinetic agent, can induce natural bowel movements by enhancing gastrointestinal motility and colonic transit in patients with chronic constipation and irritable bowel syndrome with constipation. This 3-part phase 1 study evaluated the safety, tolerability, and pharmacokinetic and pharmacodynamic profiles of DSP-6952. Eighty-eight Japanese subjects (64 healthy volunteers and 24 subjects with spontaneous bowel movements ≤3 times/wk) were randomized to DSP-6952 or placebo. The overall incidence of treatment-emergent adverse events (TEAEs) was similar for DSP-6952 and placebo. The most frequent TEAEs were gastrointestinal disorders; diarrhea was more common with DSP-6952, but only when it was administered to healthy volunteers. Peak plasma concentration (Cmax ) and area under the concentration-time curve (AUC) of DSP-6952 were dose-proportional within a range of 4-120 mg. Under fed conditions, the Cmax and AUC of DSP-6952 were approximately half those of fasting conditions. No abnormal drug accumulation was observed with repeated administration. In subjects with spontaneous bowel movements ≤3 times/wk, the median change in the frequency of bowel movements from baseline increased, although the difference did not reach statistical significance. DSP-6952 was well tolerated at single and multiple doses up to 120 mg/d, with a linear pharmacokinetic profile among all subjects.

The objectives of the present study were to evaluate the bioequivalence of 2 tablet formulations of prucalopride, generic and branded, and to investigate relevant pharmacokinetic and safety profiles. This study was designed as a randomized, open-label, fasting, single-dose, crossover, and dual-period trial. After overnight fasting, 12 subjects were given prucalopride tablets via oral administration, and blood specimens were obtained up to 96 hours after dosing. Prucalopride concentrations in plasma were measured using ultraprecision liquid chromatography-tandem mass spectrometry followed by calculation of pharmacokinetic parameters. The safety of prucalopride was assessed throughout the study. The pharmacokinetics of prucalopride can be defined as a 2-compartment model with a long elimination phase. No significant differences were observed between the pharmacokinetic profiles of the generic and branded prucalopride tablets. Bioequivalence was evaluated using 90%CIs for the ratio test/reference of log area under the concentration-time curve over 96 hours, log area under the concentration-time curve to infinity, and log peak concentration from generic and branded tablets, which were 100.06-109.94%, 100.63-110.32%, and 95.84-113.08%, respectively. During administration of the medication, there were 18 adverse events in 6 subjects in the test formulation group and 19 cases of adverse events in 6 subjects in the reference formulation group (P > .05). No severe adverse effects were detected. These results suggest that generic and branded prucalopride tablets are bioequivalent and show similar safety profiles.

There’s three things in this world that you need:respect for all kinds of life, a nice bowel movementon a regular basis, and a navy blazerRobin WilliamsChronic idiopathic constipation (CIC) is a fr...

Cognitive deficits commonly accompany psychiatric disorders but are often underrecognised, and difficult to treat. The 5-HT4 receptor is a promising potential treatment target for cognitive impairment because in animal studies 5-HT4 receptor agonists enhance hippocampal-dependent memory processes. To date, there has been little work translating these effects to humans. We tested whether short-term administration of the 5-HT4 partial agonist, prucalopride, modified behavioural and neural (fMRI) memory processing in 44 healthy human volunteers using an experimental medicine model. We found that participants who had received six days of prucalopride treatment were significantly better at recalling previously seen neutral images and distinguishing them from new images. At a neural level, prucalopride bilaterally increased hippocampal activity and activity in the right angular gyrus compared with placebo. Taken together, these findings demonstrate the potential of 5-HT4-receptor activation for cognitive enhancement in humans, and support the potential of this receptor as a treatment target for cognitive impairment.

A series of oxadiazole derivatives were synthesized and evaluated as 5-hydroxytryptamine-4 receptor (5-HT

More than 30% of all pharmaceuticals target G-protein-coupled receptors (GPCRs). Here, we present a GPCR-based screen in yeast to identify ligands for human serotonin receptor 4 (5-HTR

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by memory decline and impaired hippocampal synaptic plasticity. The serotonin 5-HT4 receptor is involved in learning and memory processes. This study explored the effects of chronic stimulation of 5-HT4R on cognition, memory, long-term potentiation (LTP), paired-pulse ratio (PPR), and neuronal apoptosis in a rat model of amyloid-beta (Aβ)-induced AD. Thirty-five male Wistar rats were randomly divided into three groups as follows: the sham, Aβ, and Aβ + BIMU8 groups. Aβ (6 µg/µl) was administrated by intracerebroventricular (icv) injection. The animals were treated with BIMU8 (1 μg/μL, ICV) as a 5-HT4R agonist for 30 days. Memory and behavioral changes were assessed by the passive avoidance learning, novel object recognition, open field, and elevated plus maze tests. Hippocampal synaptic plasticity was evaluated in the dentate gyrus (DG) in response to the stimulation applied to the perforant pathway. Furthermore, neuronal apoptosis was measured in the hippocampus. Data were analyzed by SPSS version 19 using one-way ANOVA, followed by Tukey’s post hoc test. Aβ induced memory deficits and neuronal loss and inhibited LTP induction. Aβ also increased the normalized PPR. BIMU8 enhanced the slope of the field excitatory postsynaptic potential in LTP and improved cognition behavior. Paired-pulse inhibition or facilitation was not affected by LTP induction in Aβ animals receiving the BIMU8. It can be concluded that the stimulation of the 5-HT4 receptor modulated the Aβ-induced cognition and memory deficits, probably via a decrease in the hippocampal apoptotic neurons and an improvement in the hippocampal synaptic functions without involving its inhibitory interneurons.

BACKGROUND Tegaserod, a serotonin (5-HT4) agonist initially approved for constipation but withdrawn from use in 2007 because of concerns about cardiovascular adverse effects, was resubmitted to the Food and Drug Administration (FDA) in 2018 for use in a restricted population. AREAS OF UNCERTAINTY Despite an 18-year regulatory history, there remain pharmacology and clinical trial concerns that have not been addressed but are critical for proper assessment of the drug safety and efficacy profile. SOURCES Original FDA reviews, FDA and developer advisory committee briefing documents, and published literature. RESULTS The major pharmacology concern is that the fate and effects of half of the molecule, the pentylaminoguanidine moiety, are unknown. There is evidence that pentylaminoguanidine may contribute to both efficacy and safety. There are other metabolites that are poorly characterized, and potential receptor interactions that suggest cardiovascular effects are possible. The major clinical trial concern is that, while the trial data support a low but definite cardiovascular risk, both subject follow-up and cardiovascular event descriptions were incomplete such that an accurate estimate of cardiovascular risk is not possible. CONCLUSIONS The uncertainties and lack of reliable evidence regarding tegaserod metabolism and cardiovascular risk estimates may discourage clinical use. Signals for cardiovascular toxicity in typical drug development programs are subtle and must be pursued aggressively, with complete case follow-up and cardiovascular event capture in the clinical trials.

Aim: To synthesize the new bioactive metabolites of mosapride (R)-N-[2-hydroxy-3-(4-fluorobenzyl)amino]-propyl-5-chlorine-4-amino-2-ethoxyben-zamide (R-isomer) and (S)-N-[2-hydroxy-3-(4-fluorobenzyl)amino]-propyl-5-chlorine-4-amino-2-ethoxybenzamide (S-isomer) and evaluate their in vitro and in vivo pharmacological and pharmacokinetic profiles. Results: S-isomer as a gastroprokinetic agent showed significant pharmacological activities in vivo. Furthermore, compared with the EC50 values for R-isomer and mosapride, S-isomer was proven to generate the same 5-HT4 receptor agonistic activity with a smaller amount. S-isomer exhibited significant differences in the pharmacokinetic properties, which indicate that higher absorption rate and extent compared with R-isomer. Conclusion: S-isomer might have great potential as a safe and effective prokinetic agent capable of lessening gastrointestinal symptoms and increasing quality of life.

SUVN-D4010 is a novel, potent, highly selective 5-HTSingle-ascending dose and multiple-ascending dose studies for 14 days were conducted in healthy adults using a randomized, double-blind design. The effects of food, sex, and age on SUVN-D4010 pharmacokinetics (25 mg single dose) were evaluated using an open-label, two-period, randomized, fed and fasted, crossover design. Pharmacokinetics and safety assessments were conducted throughout the study.SUVN-D4010 at a single dose up to 45 mg and multiple doses up to 40 mg once daily was found to be safe and well tolerated in healthy adults. The most frequently reported adverse events were headache and nausea. SUVN-D4010 exposure was dose proportional across the tested doses. Steady state was achieved on day 2 after once-daily dosing for 14 days. Food had no significant effect on the exposures but an increase in median time to attain the maximum plasma concentration (tSUVN-D4010 was found to be safe and well tolerated in healthy human subjects. SUVN-D4010 followed linear pharmacokinetics across the dose range. Accumulation was in the range of 1.3- to 1.4-fold after multiple dosing. Renal excretion is not the major route of elimination. Food had no effect on the exposures but increased the t

Alzheimer’s disease (AD) is a neurodegenerative disorder whose prevalence has an incidence in senior citizens. Unfortunately, current pharmacotherapy only offers symptom relief for patients with side effects such as bradycardia, nausea, and vomiting. Therefore, there is a present need to provide other therapeutic alternatives for treatments for these disorders. The 5-HT4 receptor is an attractive therapeutic target since it has a potential role in central and peripheral nervous system disorders such as AD, irritable bowel syndrome, and gastroparesis. Quantitative structure-activity relationship analysis of a series of 62 active compounds in the 5-HT4 receptor was carried out in the present work. The structure-activity relationship was estimated using three-dimensional quantitative structure-activity relationship (3D-QSAR) techniques based on these structures’ field molecular (force and Gaussian field). The best force-field QSAR models achieve a value for the coefficient of determination of the training set of R2training = 0.821, and for the test set R2test = 0.667, while for Gaussian-field QSAR the training and the test were R2training = 0.898 and R2test = 0.695, respectively. The obtained results were validated using a coefficient of correlation of the leave-one-out cross-validation of Q2LOO = 0.804 and Q2LOO = 0.886 for force- and Gaussian-field QSAR, respectively. Based on these results, novel 5-HT4 partial agonists with potential biological activity (pEC50 8.209–9.417 for force-field QSAR and 9.111–9.856 for Gaussian-field QSAR) were designed. In addition, for the new analogues, their absorption, distribution, metabolism, excretion, and toxicity properties were also analyzed. The results show that these new derivatives also have reasonable pharmacokinetics and drug-like properties. Our findings suggest novel routes for the design and development of new 5-HT4 partial agonists.

5-HT

It is unclear whether metoclopramide and domperidone act on human cardiac serotonin 5-HT

BACKGROUND Gastric motor function alterations have been implicated in the pathogenesis of functional dyspepsia with postprandial distress syndrome (PDS). Prucalopride, a 5-TH4 agonist, is known to stimulate gastrointestinal motility. We aimed to evaluate the effect of prucalopride on gastric sensorimotor function in healthy subjects (HV). METHODS Barostat and intragastric pressure (IGP) measurements were performed in 17 HV (59% females, age 29.4 ± 2.7 y) after treatment with placebo or prucalopride (2 mg) (single-blind cross-over). Isobaric stepwise distensions and gastric sensations were assessed to determine gastric compliance and sensitivity. Gastric accommodation (GA) with the barostat was quantified before and after ingestion of 200 ml of a nutrient drink (ND). GA measured by IGP was quantified as the drop of IGP from baseline during the intragastric infusion of ND until maximal satiation (60 ml/min). KEY RESULTS Prucalopride did not affect barostat assessed gastric compliance or sensitivity. No differences were observed in GA after prucalopride. During the barostat study, 10 min after the meal, 7 HVs reported significantly higher ratings for nausea after prucalopride (p

Background Opioid-induced respiratory compromise remains a significant challenge in etorphine-immobilised wildlife. Serotonergic agonists offer a potential avenue for preventing or treating opioid-induced respiratory compromise. We therefore aimed to determine whether the selective 5-hydroxytryptamine receptor 4 (5-HT4) agonist, BIMU-8, reverses opioid-induced respiratory compromise in etorphine-immobilised goats. Methods Seven healthy adult goats were immobilised with etorphine, then treated with BIMU-8 or sterile water 5 minutes later in a randomised, prospective cross-over study. Cardiorespiratory variables were measured at 1-minute intervals from 4 minutes before etorphine to 15 minutes after its administration. Arterial blood gas analyses were also performed before and after etorphine administration and the respective treatments. Results Intravenous injection of BIMU-8 attenuated etorphine-induced respiratory compromise, as indicated by improvements, compared to baseline and between treatments, in respiratory rate (ƒR ), peripheral arterial blood oxygen saturation (SpO2 ), partial pressure of arterial oxygen (PaO2 ) and the alveolar-arterial oxygen partial pressure gradient (P(A-a)O2 ). BIMU-8 caused an increase in heart rate and a temporary decrease in arterial blood pressure. Mild movements and slight muscle spasm occurred but BIMU-8 did not reverse immobilisation. Conclusion Our results indicate that BIMU-8 may be a potential drug candidate for the treatment, or prevention, of etorphine-induced respiratory compromise in immobilised ungulates.

Background Postoperative ileus is common and is a major clinical problem. It has been widely studied in patients and in experimental models in laboratory animals. A wide variety of treatments have been tested to prevent or modify the course of this disorder. Purpose This review draws together information on animal studies of ileus with studies on human patients. It summarizes some of the conceptual advances made in understanding the mechanisms that underlie paralytic ileus. The treatments that have been tested in human subjects (both pharmacological and non-pharmacological) and their efficacy are summarized and graded consistent with current clinical guidelines. The review is not intended to provide a comprehensive overview of ileus, but rather a general understanding of the major clinical problems associated with it, how animal models have been useful to elucidate key mechanisms and, finally, some perspectives from both scientists and clinicians as to how we may move forward with this debilitating yet common condition.

OBJECTIVES Chronic constipation (CC) is a recurrent functional bowel disorder worldwide. The purpose of this study is to examine its pooled placebo response rate and compare placebo response level in randomized controlled trials (RCTs) with different endpoint assessments. METHODS PubMed, Cochrane Library, and Embase were electronically searched for therapeutic RCTs of CC with placebo control. Data extraction and assessment of risk of bias were performed independently by 2 reviewers. All the statistical calculation and analysis were performed using R 3.6.0. Our protocol has registered in PROSPERO with registration number: CRD42019121287. RESULTS There were 46 studies included with 5,992 constipated patients allocated to the placebo arm in total. The pooled placebo response rate was 28.75% (95% confidence interval: 23.83%-33.67%) with significant heterogeneity among trials ((Equation is included in full-text article.)= 93.6%). Treatment efficacy assessed using subjective improvement had a significantly higher placebo response rate than that assessed with improvement in complete (spontaneous) bowel movements or composite improvement (41.40% vs 18.31% or 20.35%, P < 0.001). According to the results of meta-regression, active treatment and endpoint assessment were most likely to lead to the huge heterogeneity among studies. DISCUSSION Patients with CC have significant response level to placebo. Based on findings in this study, we do not recommend subjective improvement as endpoint while designing therapeutic RCTs for chronic constipated patients.

Background and aim Prucalopride, a high-affinity 5-hydroxytryptamine 4 receptor agonist, promotes esophageal peristalsis, while phosphodiesterase type 5 inhibitor sildenafil inhibits esophageal peristalsis. The present study was aimed to evaluate whether prucalopride would augment esophageal peristalsis subsequent to the application of sildenafil. Methods Seventeen healthy adults underwent high-resolution manometry by a catheter with one injection port located in the mid-esophagus. Secondary peristalsis was assessed by rapid air injections after water swallows. Two sessions were randomly performed including acute administration of sildenafil 50 mg after pretreatment with prucalopride or the placebo. Results The frequency of primary peristalsis subsequent to the administration of sildenafil was significantly increased by prucalopride (P = 0.02). Prucalopride also significantly increased distal contractile integral of primary peristalsis subsequent to the administration of sildenafil (P = 0.03). No difference in the frequency of secondary peristalsis subsequent to the administration of sildenafil for air injects of 10 mL (P = 0.14) or 20 mL (P = 0.21) was found between prucalopride and placebo. Prucalopride did not change distal contractile integral of secondary peristalsis subsequent to the administration of sildenafil for air injections of 10 mL (P = 0.09) or 20 mL (P = 0.12). Conclusions Prucalopride modulates sildenafil-induced inhibition of primary peristalsis by increasing its effectiveness and peristaltic wave amplitude. Our findings suggest that activation of 5-hydroxytryptamine 4 receptors plays a role in mediating sildenafil-induced inhibition of esophageal primary peristalsis rather than secondary peristalsis.

Ongoing activity in nociceptors, a driver of spontaneous pain, can be generated in dorsal root ganglion neurons in the absence of sensory generator potentials if one or more of three neurophysiological alterations occur - prolonged depolarization of resting membrane potential (RMP), hyperpolarization of action potential (AP) threshold, and/or increased amplitude of depolarizing spontaneous fluctuations of membrane potential (DSFs) to bridge the gap between RMP and AP threshold. Previous work showed that acute, sustained exposure to serotonin (5-HT) hyperpolarized AP threshold and potentiated DSFs, leading to ongoing activity if a separate source of maintained depolarization was present. Cellular signaling pathways that increase DSF amplitude and promote ongoing activity acutely in nociceptors are not known for any neuromodulator. Here, isolated DRG neurons from male rats were used to define the pathway by which low concentrations of 5-HT enhance DSFs, hyperpolarize AP threshold, and promote ongoing activity. A selective 5-HT(4) receptor antagonist blocked these 5-HT-induced hyperexcitable effects, while a selective 5-HT(4) agonist mimicked the effects of 5-HT. Inhibition of cAMP effectors, protein kinase A (PKA) and exchange protein activated by cAMP (EPAC), attenuated 5-HT’s hyperexcitable effects, but a blocker of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels had no significant effect. 5-HT(4)-dependent PKA activation was specific to DRG neurons that bind isolectin B4 (a nonpeptidergic nociceptor marker). 5-HT’s effects on AP threshold, DSFs, and ongoing activity were mimicked by a cAMP analog. Sustained exposure to 5-HT promotes ongoing activity in nonpeptidergic nociceptors through the G(s)-coupled 5-HT(4) receptor and downstream cAMP signaling involving both PKA and EPAC.

BACKGROUND: 5-HT(4) receptor (5-HT(4)R) agonists exert prokinetic actions in the GI tract, but non-selective actions and potential for stimulation of non-target 5-HT(4)Rs have limited their use. Since 5-HT(4)Rs are expressed in the colonic epithelium and their stimulation accelerates colonic propulsion in vitro, we tested whether luminally acting 5-HT(4)R agonists promote intestinal motility. METHODS: Non-absorbed 5-HT(4)R agonists, based on prucalopride and naronapride, were assessed for potency at the 5-HT(4)R in vitro, and for tissue and serum distribution in vivo in mice. In vivo assessment of prokinetic potential included whole gut transit, colonic motility, fecal output, and fecal water content. Colonic motility was also studied ex vivo in mice treated in vivo. Immunofluorescence was used to evaluate receptor distribution in human intestinal mucosa. KEY RESULTS: Pharmacological screening demonstrated selectivity and potency of test agonists for 5-HT(4)R. Bioavailability studies showed negligible serum detection. Gavage of agonists caused faster whole gut transit and colonic motility, increased fecal output, and elevated fecal water content. Prokinetic actions were blocked by a 5-HT(4)R antagonist, and were not detected in 5-HT(4)R knockout mice. Agonist administration promoted motility in models of constipation. Evaluation of motility patterns ex vivo revealed enhanced contractility in the middle and distal colon. Immunoreactivity for 5-HT(4)R is present in the epithelial layer of the human small and large intestines. CONCLUSIONS AND INFERENCES: These findings demonstrated that stimulation of epithelial 5-HT(4)Rs can potentiate propulsive motility, and support the concept that mucosal 5-HT(4)Rs could represent a safe and effective therapeutic target for the treatment of constipation.

BACKGROUND Gastroparesis, defined by delayed gastric emptying in the absence of mechanical outlet obstruction, is a frequent neuropathic complication of diabetes mellitus, and effective treatments are lacking. Prucalopride is a pan-gut prokinetic with selective agonist effects on serotonin 5-HT4 receptors in the gut. This study aimed to assess the effect of prucalopride 4 mg daily on Gastroparesis Cardinal Symptom Index (GCSI), meal-related symptom score (MRSS), and gastric emptying rate in diabetic or connective tissue disease (CTD)-related gastroparesis patients. METHODS This was a double-blind crossover trial of four-week treatment periods with prucalopride or placebo divided by two weeks of washout. GSCI, MRSS, gastric emptying scintigraphy, PAGI-SYM, and PAGI-QoL were assessed at baseline and the end of each treatment period. Daily bowel movement (BM) frequency and gastrointestinal symptoms were recorded in each period. KEY RESULTS Fifteen gastroparesis patients (13 diabetic, 2 CTD) were enrolled. GCSI scores were lower than baseline but not different between treatment arms. MRSS scores over time or cumulative score were not significantly different between groups. Gastric emptying was more rapid in the prucalopride treatment period, with mean four-hour meal retention of 22 ± 6% in PRU period vs 40 ± 9% in the placebo period (P = 0.05). Weekly BM frequency was significantly higher in prucalopride than placebo periods (10.5 ± 1.8 vs 7.5 ± 0.8, P

Increasing evidence shows the close relationship between hippocampal glutamatergic and serotonergic systems through the modulation of behavioral responses. This study aimed to investigate the possible involvement of 5-HT

Introduction: Tegaserod, an orally active, potent 5-hydroxytryptamine-4 serotonin receptor agonist, was previously indicated for irritable bowel syndrome but was voluntarily withdrawn due to potential cardiovascular side effects. In vitro studies suggested that tegaserod increased platelet aggregation, but these results were not reproduced or were inconclusive. We sought to assess ex vivo effects of tegaserod on platelet aggregation. Methods: In this double-blind, placebo-controlled, crossover study, we randomized a majority of healthy patients with no history of cardiovascular risk factors (n = 21) to receive tegaserod or matching placebo for 7 + 2 days followed by a 7- to 10-day washout period, and then patients were crossed over to the other study drug for the next 7 + 2 days. Unstimulated and agonist-stimulated platelet aggregation; P-selectin expression; serum thromboxane (Tx)B2 and urinary 11-dehydro (11-dh) TxB2; and tegaserod and M29.0 concentrations were serially assessed. Results: There was no significant difference in percentage change in unstimulated or adenosine diphosphate (ADP)- and ADP + serotonin-, collagen- and thrombin receptor activating peptide–induced maximum platelet aggregation and in platelet P-selectin expression in the presence of tegaserod at any time point when compared to placebo. Similarly, there was no significant difference in percentage change in serum TxB2 or urinary 11-dhTxB2 levels between placebo and tegaserod. No new or unexpected findings were observed in evaluations of safety or pharmacokinetic parameters. Conclusion: This comprehensive pharmacodynamic study, by employing established markers used in prior investigations, which have been considered by the Food and Drug Administration to indicate drug-related platelet effects, does not demonstrate any influence of tegaserod treatment on platelet function.

Objective Post dural puncture headache (PDPH) is a common complication in patients following diagnostic or therapeutic lumbar puncture, procedures requiring epidural access, and spinal surgery. Epidural blood patch (EBP), the gold standard for the treatment of this pathology requires training not provided to emergency physicians. In addition, the presence of concomitant pathology and abnormal laboratory values are contraindications to perform EBP. In presence of these limitations, we sought for a non-interventional management of PDPH utilizing high-flow oxygen and pro-serotonin agents. We reviewed the mechanism of action of this therapy Methods To illustrate our proposal, we report a series of twelve consecutive patients with PDPH treated with high-flow oxygen therapy at 12 L/min via a non-rebreathing mask and intravenous metoclopramide. Results All patients were treated with this conservative therapy, no adverse reactions were observed. After the intervention, the headache resolved without further indications for PDPH. Conclusion Our series suggests that combining high-flow oxygen and pro-serotonin agents such metoclopramide in the ED might be a feasible option as effective as the invasive methods used in treating PDPH. This therapy appears to be efficient and to minimize risk, cost and side effects. It presents an easily accessible alternative that should be considered when PDPH is not a viable option.

Numerous chemotypes have been described over time in order to generate potent and selective 5-HTThis review summarizes the patent applications from 2014 to present, dedicated to the use or the description of novel 5-HTThe therapeutic potential of 5-HT

Animal experimental studies suggest that 5-HT4 receptor activation holds promise as a novel target for the treatment of depression and cognitive impairment. 5-HT4 receptors are post-synaptic receptors that are located in striatal and limbic areas known to be involved in cognition and mood. Consistent with this, 5-HT4 receptor agonists produce rapid antidepressant effects in a number of animal models of depression, and pro-cognitive effects in tasks of learning and memory. These effects are accompanied by molecular changes, such as the increased expression of neuroplasticity-related proteins that are typical of clinically useful antidepressant drugs. Intriguingly, these antidepressant-like effects have a fast onset of their action, raising the possibility that 5-HT4 receptor agonists may be a particularly useful augmentation strategy in the early stages of SSRI treatment. Until recently, the translation of these effects to humans has been challenging. Here, we review the evidence from animal studies that the 5-HT4 receptor is a promising target for the treatment of depression and cognitive disorders, and outline a potential pathway for the efficient and cost-effective translation of these effects into humans and, ultimately, to the clinic.

Minesapride is a novel 5-hydroxytryptamine 4 (5-HT

Constipation is common in patients with Parkinson's disease (PD). Due to the considerable negative outcomes of constipation, significant efforts have been made to prevent and manage chronic constipation in these patients.Herein, the authors review some of the known pathophysiological causes for slow gastrointestinal (GI) transit in PD patients and the different pharmacological options. All relevant clinical and experimental data found through online databases were included. Bulking agents, osmotic and stimulant laxatives, chloride channel activators, ghrelin agonists, 5-HT4 receptor agonists, and probiotics are some of the proposed medicinal agents. of the authors further review the evidence on alpha-synuclein and botulinum neurotoxin in these patients. It should be noted, however, that some of these interventions are required to be further validated.Reduction of GI transit and dysfunction of the anorectum is obvious in PD, affecting the incidence of constipation and thus, quality of life (QOL). Furthermore, due to an inadequate and delayed absorption of oral anti PD medications, dose adjustments and changes in the route of administration are recommended.

Muscarinic receptor 1 positive allosteric modulators (M1PAMs) enhance colonic propulsive contractions and defecation through the facilitation of M1 receptor (M1R)-mediated signaling. We examined M1R expression in the colons of 5 species and compared colonic propulsion and defecation caused by the M1PAM, T440, the 5-HTM1R expression was profiled by immunostaining and in situ hybridization. In vivo studies utilized male SD rats and beagle dogs. Colonic propulsive contractions were recorded by manometry in anesthetized rats. Gut contractions in dogs were assessed using implanted force transducers in the ileum, proximal, mid, and distal colons.M1R was localized to neurons of myenteric and submucosal plexuses and the epithelium of the human colon. A similar receptor localization was observed in rat, dog, mouse, and pig. T440 enhanced normal defecation in rats in a dose-dependent manner. Prucalopride also enhanced defecation in rats, but the maximum effect was half that of T440. Neostigmine and T440 were similarly effective in enhancing defecation, but the effective dose of neostigmine was close to its lethal dose. In rats, all 3 compounds induced colonic contractions, but the associated propulsion was strongest with T440. In dogs, intestinal contractions elicited by T440 propagated from ileum to distal colon. Prucalopride and neostigmine also induced intestinal contractions, but these were less well coordinated. No loss of effectiveness of T440 on defecation occurred after 5 days of repeated dosing.These results suggest that M1PAMs produce highly coordinated propagating contraction by actions on the enteric nervous system of the colon. The localization of M1R to enteric neurons in both animals and humans suggests that the M1PAM effects would be translatable to human. M1PAMs provide a potential novel therapeutic option for constipation disorders.

Enteric serotonin may function as a mucosal growth factor. Previous work demonstrated increased crypt cell proliferation and intestinal mucosal surface area with potentiation of serotonin. While an indirect mechanism was postulated to explain these effects, the presence of 5-HT4 receptors on enterocytes raises the possibility of a direct action of serotonin. We hypothesized that a 5-HT4 specific agonist, prucalopride, would stimulate intestinal mucosal growth and enhance absorptive function in the murine small intestine. Adult wild-type mice were treated parenterally with prucalopride for 14 days via surgically implanted osmotic pumps. In vivo d-xylose absorption was assessed by oral gavage and serum d-xylose measurements. On day 14, glucose absorption was assessed by instilling a glucose solution into isolated segments of small intestine. The bowel was harvested and examined for morphologic parameters and crypt cell proliferation. Villus height, crypt depth, and crypt proliferation were significantly increased in the distal small bowel of prucalopride-treated mice compared with control animals. Crypt depth was also increased in the proximal and middle small intestine in treated mice. There was no difference in d-xylose absorption throughout the study period; however, glucose absorption was significantly increased in the distal small intestine of prucalopride-treated mice. Parenteral administration of the 5-HT4 receptor specific agonist, prucalopride, results in morphologic and functional changes in the murine small intestine that are most prominent in the distal small bowel. While further studies are necessary to delineate the mechanism, it is plausible that the effects are mediated by 5-HT4 receptors on enterocytes.

Minesapride (drug code: DSP-6952) is a potential gastrointestinal prokinetic agent with high selectivity for 5-hydroxytryptamine 4 (5-HT

Patients with chronic constipation benefit from treatment with 5-hydroxytryptamine 4 (5-HT4) receptor agonists. However, the first-generation 5-HT4 receptor agonists cisapride and tegaserod were withdrawn from the market owing to rare cardiovascular adverse events that were not 5-HT4-receptor-related but due to the lack of selectivity of these drugs. Here we report the nonclinical cardiovascular profile of the selective 5-HT4 receptor agonist prucalopride. To assess its non-5-HT4 receptor-mediated effects on cardiovascular electrophysiological parameters, in vitro studies were performed in human ether-a-go-go-related gene-transfected cells, guinea pig ventricular myocytes and papillary muscle preparations, rabbit and dog Purkinje fibers, and the Langendorff rabbit heart. In vivo experiments were performed in a rabbit model for drug-induced proarrhythmogenesis, in anesthetized guinea pigs, and anesthetized and conscious dogs. In addition, human platelet aggregation and coronary artery contraction were studied to exclude interactions that have been suggested to mediate the cardiovascular effects of tegaserod. Effects at 5-HT4 receptors were evaluated in piglet and human atrial myocardium, and in anesthetized pigs. Finally, cardiovascular endpoints were investigated in chronic, repeated-dose toxicology studies at very high prucalopride doses in rats and dogs. No relevant effects were observed in any of the cardiovascular studies at concentrations at least 50 times the therapeutic plasma level. Only in pigs were minor and transient increases in heart rate and blood pressure noted upon first exposure to prucalopride, at plasma levels at least 10 times higher than human therapeutic plasma levels. Prucalopride may thus provide therapeutic benefit without the cardiovascular risks reported for other 5-HT4 receptor agonists.

The serotonergic neurotransmitter system has been widely implicated in the pathophysiology of mood-related disorders such as anxiety and major depressive disorder (MDD). The onset of therapeutic efficacy of traditional antidepressants is delayed by several weeks. The 5-HT4 receptor has emerged as a new therapeutic target since agonists of this receptor induce rapid antidepressant-like responses in rodents. Here we show that the 5-HT4 receptor is regulated by CK2, at transcriptional and post-transcriptional levels. We present evidence, in two different CK2α knockout mouse lines, that this regulation is region-specific, with the 5-HT4 receptor upregulated in prefrontal cortex (PFC) but not striatum or hippocampus where CK2α is also ablated. 5-HT4 receptor signaling is enhanced in vitro, as evidenced by enhanced cAMP production or receptor plasma membrane localization in the presence of CK2 inhibitor or shRNA targeting CK2α. In vivo, 5-HT4 receptor signaling is also upregulated since ERK activation is elevated and sensitive to the inverse agonist, GR113808 in the PFC of CK2α KO mice. Behaviorally, KO mice as well as mice with AAV-mediated deletion of CK2α in the PFC show a robust 'anti-depressed-like' phenotype and display an enhanced response to antidepressant treatment when tested in paradigms for mood and anxiety. Importantly, it is sufficient to overexpress the 5-HT4 receptor in the mPFC to generate mice with a similar 'anti-depressed-like' phenotype. Our findings identify the mPFC as the region that mediates the effect of enhanced 5-HT4 receptor activity and CK2 as modulator of 5-HT4 receptor levels in this brain region that regulates mood-related phenotypes.

Postoperative ileus (POI) is an impairment of coordinated gastrointestinal (GI) motility that develops as a consequence of abdominal surgery and is a major factor contributing to patient morbidity and prolonged hospitalisation. Despite the availability of various options its treatment is still under debate. This review will focus on effect of Prucalopride (5-HT

5-HT4 receptor stimulation has pro-cognitive and antidepressant-like effects in animal experimental studies; however, this pharmacological approach has not yet been tested in humans. Here we used the 5-HT4 receptor partial agonist prucalopride to assess the translatability of these effects and characterise, for the first time, the consequences of 5-HT4 receptor activation on human cognition and emotion.Forty one healthy volunteers were randomised, double-blind, to a single dose of prucalopride (1 mg) or placebo in a parallel group design. They completed a battery of cognitive tests measuring learning and memory, emotional processing and reward sensitivity.Prucalopride increased recall of words in a verbal learning task, increased the accuracy of recall and recognition of words in an incidental emotional memory task and increased the probability of choosing a symbol associated with a high likelihood of reward or absence of loss in a probabilistic instrumental learning task. Thus acute prucalopride produced pro-cognitive effects in healthy volunteers across three separate tasks.These findings are a translation of the memory enhancing effects of 5-HT4 receptor agonism seen in animal studies, and lend weight to the idea that the 5-HT4 receptor could be an innovative target for the treatment of cognitive deficits associated with depression and other neuropsychiatric disorders. Contrary to the effects reported in animal models, prucalopride did not reveal an antidepressant profile in human measures of emotional processing.

Previously, we found that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson&rsquo, s disease (PD) model mice (PD mice) showed facilitation of hippocampal memory extinction via reduced cyclic adenosine monophosphate (cAMP)/cAMP-dependent response element-binding protein (CREB) signaling, which may cause cognitive impairment in PD. Serotonergic neurons in the median raphe nucleus (MnRN) project to the hippocampus, and functional abnormalities have been reported. In the present study, we investigated the effects of the serotonin 5-HT4 receptor (5-HT4R) agonists prucalopride and velusetrag on the facilitation of memory extinction observed in PD mice. Both 5-HT4R agonists restored facilitation of contextual fear extinction in PD mice by stimulating the cAMP/CREB pathway in the dentate gyrus of the hippocampus. A retrograde fluorogold-tracer study showed that &gamma, aminobutyric acid-ergic (GABAergic) neurons in the reticular part of the substantia nigra (SNr), but not dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNpc), projected to serotonergic neurons in the MnRN, which are known to project their nerve terminals to the hippocampus. It is possible that the degeneration of the SNpc DAergic neurons in PD mice affects the SNr GABAergic neurons, and thereafter, the serotonergic neurons in the MnRN, resulting in hippocampal dysfunction. These findings suggest that 5HT4R agonists could be potentially useful as therapeutic drugs for treating cognitive deficits in PD.

Functional constipation is common in children and adults worldwide. Functional constipation shows similarities in children and adults, but important differences also exist regarding epidemiology, symptomatology, pathophysiology, diagnostic workup and therapeutic management. In children, the approach focuses on the behavioural nature of the disorder and the initial therapeutic steps involve toilet training and laxatives. In adults, management focuses on excluding an underlying cause and differentiating between different subtypes of functional constipation - normal transit, slow transit or an evacuation disorder - which has important therapeutic consequences. Treatment of adult functional constipation involves lifestyle interventions, pelvic floor interventions (in the presence of a rectal evacuation disorder) and pharmacological therapy. When conventional treatments fail, children and adults are considered to have intractable functional constipation, a troublesome and distressing condition. Intractable constipation is managed with a stepwise approach and in rare cases requires surgical interventions such as antegrade continence enemas in children or colectomy procedures for adults. New drugs, including prokinetic and prosecretory agents, and surgical strategies, such as sacral nerve stimulation, have the potential to improve the management of children and adults with intractable functional constipation.

The prokinetic effects of 5-HT

Prucalopride, a high affinity, selective serotonin type 4 (5-HT4) receptor agonist, was associated with increased neoplasia incidence (in endocrine tissues and liver) in 2-year rodent bioassays, without evidence of a genotoxic mechanism of action. Proposed mechanisms of action involve prolactin and the constitutive androstane receptor (CAR). Epigenetic mechanisms and their relevance to humans are discussed. Data from in vitro and in vivo rodent studies demonstrated that prucalopride-related stimulation of prolactin secretion (via dopamine receptor D2 antagonism at high doses) is a rodent-specific, non-genotoxic mechanism for inducing hyperplasia and neoplasia in prolactin receptor-expressing endocrine tissues. Additional data demonstrated that CAR-mediated liver enzyme induction underlies the observed hepatocellular adenomas and thyroid follicular adenomas in rodents. A 12-month neonatal mouse carcinogenicity study confirmed the lack of a genotoxic mechanism of action. Furthermore, tumors were observed only at very high exposures (200 and 63 fold higher in mice and rats, respectively, than human exposure after a daily therapeutic dose of 2 mg). The studies indicate that non-genotoxic, rodent-specific, epigenetic mechanisms that are considered clinically irrelevant are responsible for the increased incidence of neoplasias associated with very high exposure to prucalopride in rodents, and that prucalopride does not pose a carcinogenic safety risk to humans.

The latest estimates from world health organization suggest that more than 450 million people are suffering from depression and other psychiatric conditions. Of these, 50-60% have been reported to have progression of gut diseases. In the last two decades, researchers introduced incipient physiological roles for serotonin (5-HT) receptors (5-HTRs), suggesting their importance as a potential pharmacological target in various psychiatric and gut diseases. A growing body of evidence suggests that 5-HT systems affect the brain-gut axis in depressive patients, which leads to gut comorbidity. Recently, preclinical trials of 5-HT4R agonists and antagonists were promising as antipsychotic and prokinetic agents. In the current review, we address the possible pharmacological role and contribution of 5-HT4R in the pathophysiology of chronic depression and associated gut abnormalities. Physiologically, during depression episodes, centers of the sympathetic and parasympathetic nervous system couple together with neuroendocrine systems to alter the function of hypothalamic-pituitary-adrenal (HPA) axis and enteric nervous system (ENS), which in turn leads to onset of gastrointestinal tract (GIT) disorders. Consecutively, the ENS governs a broad spectrum of physiological activities of gut, such as visceral pain and motility. During the stages of emotional stress, hyperactivity of the HPA axis alters the ENS response to physiological and noxious stimuli. Consecutively, stress-induced flare, swelling, hyperalgesia and altered reflexes in gut eventually lead to GIT disorders. In summary, the current review provides prospective information about the role and mechanism of 5-HT4R-based therapeutics for the treatment of depressive disorder and possible consequences for the gut via brain-gut axis interactions. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

Enhancing stress resilience could protect against stress-induced psychiatric disorders in at-risk populations. We and others have previously reported that (R,S)-ketamine acts as a prophylactic against stress when administered 1 week before stress. While we have shown that the selective 5-hydroxytryptamine (5-HT) (serotonin) reuptake inhibitor (SSRI) fluoxetine (Flx) is ineffective as a prophylactic, we hypothesized that other serotonergic compounds such as serotonin 4 receptor (5-HT(4)R) agonists could act as prophylactics. We tested if three 5-HT(4)R agonists with varying affinity could protect against stress in two mouse strains by utilizing chronic corticosterone (CORT) administration or contextual fear conditioning (CFC). Mice were administered saline, (R,S)-ketamine, Flx, RS-67,333, prucalopride, or PF-04995274 at varying doses, and then 1 week later were subjected to chronic CORT or CFC. In C57BL/6N mice, chronic Flx administration attenuated CORT-induced weight changes and increased open-arm entries in the elevated plus maze (EPM). Chronic RS-67,333 administration attenuated CORT-mediated weight changes and protected against depressive- and anxiety-like behavior. In 129S6/SvEv mice, RS-67,333 attenuated learned fear in male, but not female mice. RS-67,333 was ineffective against stress-induced depressive-like behavior in the forced swim test (FST), but prevented anxiety-like behavior in both sexes. Prucalopride and PF-04995274 attenuated learned fear and decreased stress-induced depressive-like behavior. Electrophysiological recordings following (R,S)-ketamine or prucalopride administration revealed that both drugs alter AMPA receptor-mediated synaptic transmission in CA3. These data show that in addition to (R,S)-ketamine, 5-HT(4)R agonists are also effective prophylactics against stress, suggesting that the 5-HT(4)R may be a novel target for prophylactic drug development.

Facing the complexity of Alzheimer's disease (AD), it is now currently admitted that a therapeutic pleiotropic intervention is needed to alter its progression. Among the major hallmarks of the disease, the amyloid pathology and the oxidative stress are closely related. We propose in this study to develop original Multi-Target Directed Ligands (MTDL) able to impact at the same time Aβ protein accumulation and toxicity of Reactive Oxygen Species (ROS) in neuronal cells. Such MTDL were obtained by linking on a central piperidine two scaffolds of interest: a typical aminochlorobenzophenone present in numerous 5-HT