Effects of mosapride citrate, a 5-HT4 receptor agonist, on colonic motility in conscious guinea pigs

Ameliorative effects of the mixed aqueous extract of Aurantii Fructus Immaturus and Magnoliae Officinalis Cortex on loperamide-induced STC mice

Aurantii fructus immaturus (AFI) and Magnoliae Officinalis Cortex (MOC) have been used to treat constipation in China for thousands of years. In this study, a mouse model of slow transit constipation (STC) was established by gavage of loperamide at a dose of 10 mg/kg bw/day for seven days. Seventy-two mice were randomly allocated to six groups (control, STC model, 3 g/kg AFI + MOC, 6 g/kg AFI + MOC, 12 g/kg AFI + MOC, and mosapride). A mixed aqueous extract of AFI and MOC was administered to the STC mice at the corresponding doses from the first day of modelling. Body weight, faecal water content, gastrointestinal transit time, and intestinal propulsion rate were evaluated. Serum levels of neurotransmitters and gastrointestinal hormones, colonic expression of aquaporins (AQP), and interstitial cells of Cajal (ICC) were assessed using ELISA, immunohistochemistry, and Western blot analysis. The abundance and diversity of the gut microbiota were analysed by 16S rRNA gene sequencing. The mixed aqueous extract significantly increased faecal water content and intestinal propulsion rate and shortened gastrointestinal transit time in STC mice. Furthermore, the administration of AFI and MOC significantly decreased serum vasoactive intestinal peptide (VIP), nitric oxide (NO), and somatostatin (SS) levels and increased serum motilin (MTL) levels in STC mice. The protein expression levels of AQP3 and AQP4 in the colon tissue of STC mice significantly decreased following AFI + MOC treatment, whereas those of AQP9 significantly increased. Moreover, the AFI + MOC treatment led to an increase in the number and functionality of ICCs. In addition, the relative abundances of Ruminococcus and Oscillospira increased in response to the administration of AFI + MOC in STC mice. In conclusion, the mixed aqueous extract of AFI and MOC promoted defaecation and increased intestinal mobility in STC mice. Its mechanisms of action involve modulatory effects on neurotransmitters, gastrointestinal hormones, AQPs, and ICCs. AFI + MOC treatment also improved the diversity and abundance of the gut microbiota in STC mice, particularly short-chain fatty acid-producing bacteria, which may play an important role in its beneficial effect on constipation.

Cisapride versus Maren Pill for Functional Constipation: A Meta-Analysis

Background

The efficacy and safety of cisapride in functional constipation (FC) remain unclear. This meta-analysis aimed at investigating the efficacy and safety of cisapride and Maren pill in the treatment of FC. Material and Methods. PubMed, Web of Science, Embase, Cochrane Library, WANFANG DATA, VIP, and CNKI databases were searched from inception to December 2021 for eligible comparative studies investigating the effects and safety of cisapride and Maren pill for FC. The primary outcome was the therapeutic effectiveness rate. The secondary outcomes were recurrence rate and incidence of adverse events.

Results

A total of 526 studies were screened out by searching the electronic databases and by manually searching the relevant reference lists. According to the four-step process (identification, screening, eligibility, and inclusion) to select studies for meta-analysis, 521 articles were excluded. Finally, 5 studies with a total of 414 patients with FC were included in the quantitative analysis after sequential exclusion. The cisapride group had a significantly higher effectiveness rate than the control one (90.78% vs 64.97%, P < 0.05). The incidence of adverse events in the cisapride group was lower than that in the Maren pill group (10.08% vs 13.95%, P < 0.05). Similarly, the recurrence rate of the cisapride group was lower than that of the Maren pill group (32.31% vs 53.16%, P < 0.05).

Conclusion

For FC patients, cisapride is more effective than Maren pill; the recurrence rate and adverse event rate are lower than the latter, which makes it a better choice. The combination of cisapride and Maren pill is a direction of future research studies, which may increase the efficiency and reduce the dosage of cisapride.

Does Intravenous Ondansetron Affect the Intestinal Motility Pattern in Healthy Donkeys (Equus asinus)?

The current study was undertaken to investigate the effect of intravenous administration of ondansetron on the small and large intestinal motility in donkeys (Equus asinus) using non-invasive transabdominal ultrasonography. The current prospective, randomized, placebo-controlled, crossover study was conducted on thirty healthy donkeys (15 males and 15 females). The selected donkeys underwent two trials; the first was performed by intravenous administration of saline solution as a placebo, while the second was carried out by intravenous administration of ondansetron hydrochloride. The contractility of selected portions of both the small intestine (duodenum and jejunum) and the large intestine (left colon, right colon, and cecum) was counted over a period of 3 minutes before administration (zero time) and at 15, 30, 60, 90, 120, 180, and 240 minutes after administration. The results of this study showed that ondansetron significantly altered the small and large intestinal contractility compared to normal saline. Intravenous administration of ondansetron induced a significant decrease in the duodenal, jejunal and cecal contractility compared to placebo at 30, 60, 90, and 120 minutes after administration. Likewise, ondansetron induced a significant decrease in the left colon and right colon contractility when compared with placebo at 30, 60, 90, 120, and 180 minutes following administration. Ondansetron can be used as a highly specific and selective serotonin 5-HT₃ receptor antagonist for reducing the small and large intestinal motility in donkeys, and is therefore highly suggested for treating spasmodic colic in equine.

The tissue distribution and excretion study of mosapride and its active des-p-fluorobenzyl and 4'-N-oxide metabolites in rats by ultra-high performance liquid chromatography-tandem mass spectrometry method

1. Mosapride is a potent gastroprokinetic agent, and des-p-fluorobenzyl mosapride (M1) and mosapride-N-oxide (M2) are its two major active metabolites.2. The validated ultra-high performance liquid chromatography-tandem mass spectrometry method was successfully applied to the distribution and excretion of mosapride and its two active metabolites.3. Mosapride and its metabolites were distributed widely and rapidly in various tissues. The highest concentration of mosapride and M2 in both male and female rats was found in the duodenum, followed by cecum.4. The excretion study showed that a total of 71.8% (37.6, 22.4 and 11.8% for urine, feces and bile, respectively) and 66.3% (35.7, 22.8 and 7.8% for urine, feces and bile) of administered dose was recovered from male and female excreta. M1 was excreted in the largest dose percentage, followed by mosapride and M2, and the total cumulative excretion amounts were about 36.9, 28.1 and 11.6% in male rat, while 24.3, 25.9 and 16.2% in female rat. The results demonstrated for the first time that M2 is one of the important excretion forms of mosapride, which is much higher than that of mosapride in urine.5. This work could provide valuable information for further pharmacological and clinical studies of mosapride.

The synthesis and biological evaluation of a new bioactive metabolite of mosapride as a potential gastroprokinetic agent

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.

Electroacupuncture for Functional Constipation: A Multicenter, Randomized, Control Trial

Background and Aim. To investigate the efficacy and safety of electroacupuncture (EA) with different current intensities for functional constipation (FC) and to assess whether the effects of EA with different current intensities are superior to the mosapride. Methods. Patients with FC were randomly divided into low current intensity group (LCI), high current intensity group (HCI), and mosapride group (MC). The primary outcome was three or more spontaneous bowel movements (SBMs) per week and an increase of one or more SBMs from baseline during at least 3 of the 4 weeks. Results. The primary outcome was reached by 53.45%, 66.15%, and 52.24% of the patients who received LCI, HCI, and mosapride, respectively. EA can significantly improve the weekly SBMs and stool consistency and reduce straining severity (p < 0.0001, all). HCI improved the quality of life better than mosapride (p < 0.05) and reduced the proportion of severe constipation more than LCI and mosapride (p < 0.05, both). Conclusions. EA is effective and safe at both current intensities for FC; therapeutic effects of LCI and HCI are not superior to mosapride. EA is superior to mosapride in improving patients' life quality and satisfaction level of treatment; EA has fewer adverse events than mosapride.

Novel investigational drugs for constipation-predominant irritable bowel syndrome: a review

INTRODUCTION

Constipation-predominant irritable bowel syndrome (IBS-C) is a functional gastrointestinal (GI) disorder with an unknown etiology. A number of the drugs tested for IBS-C have also been applied to chronic constipation and chronic idiopathic constipation. Unfortunately, due to severe adverse effects, many drugs envisioned for IBS-C had been withdrawn from the market. Nevertheless, a number of potential new agents for this indication are now under development.

AREAS COVERED

The following review describes the most recently developed agents in preclinical as well as Phase 1 and Phase 2 clinical studies. Information was obtained from published literature, abstracts and the latest results found in Clinicaltrial.gov database. The authors put a special interest on glucagon-like peptide 1 analogue, bile acid modulators, serotonergic agents, guanylate cyclase C and cannabinoid antagonists.

EXPERT OPINION

To enter the market, a newly-developed drug has to meet several criteria, such as good bioavailability or the absence of drug-related adverse events. Taking into account constipation and abdominal pain as the main symptoms in IBS-C, a novel successful drug is usually able to improve both at the same time. Four out of fifteen investigational drugs described in this paper belong to the serotonergic family and have a good prognosis to reach the market; still, more long-term clinical studies are warranted.

Transcutaneous electric nerve stimulation in treatment of functional constipation: A systematic review

AIM: To evaluate the effect of transcutaneous electric nerve stimulation (TENS) on symptoms, psychology and quality of life in patients with functional constipation (FC).

METHODS: The reported studies about the efficacy of TENS in improving symptom of FC were retrieved up to May 2015 based on five English databases including PubMed, Embase, Cochrane Library, ScienceDirect, and Web of Science and four Chinese databases including China National Knowledge Infrastructure (CNKI), Wanfang Data, VIP Database and China Biology Medicine disc (CBM). The methodological quality was evaluated using the Jadad scale. Meta-analysis of eligible studies was performed using RevMan5.1. Data which were unable to convent or merge were described via descriptive analysis.

RESULTS: A total of 8 studies were included. Results of analysis indicated that: (1) TENS was superior to mosapride citrate or sham transcutaneous neuromodulation (TN) in improving the symptoms of constipation and showed the same effect as polyethylene glycol or electroacupuncture (except stool consistency) (P < 0.05); (2) TENS outperformed laxative or sham TN in accelerating colonic transit (MD = -4.62, 95%CI: -5.15--4.09, P < 0.00001); (3) Compared with electroacupuncture or sham TN, TENS could significantly reduce the anxiety and depression levels and improve the quality of life (SAS score: MD = 4.10, 95%CI: 3.53-4.67, MD = 2.77, 95%CI: 2.16-3.38, P < 0.00001; SDS score, MD = 4.22, 95%CI: 3.36-5.08, P < 0.00001).

CONCLUSION: TENS had a certain therapeutic effect on FC, and it could reduce the anxiety and depression levels and improve the quality of life of the patients. Compared with laxative or electroacupuncture, TENS is user-friendly and shows fewer side effects.

Mechanism of aqueous fructus aurantii immaturus extracts in neuroplexus of cathartic colons

AIM

To examine the effect of aqueous fructus aurantii immaturus (FAI) extracts on the intestinal plexus of cathartic colons.

METHODS

Cathartic colons were induced in rats with dahuang, a laxative used in traditional Chinese medicine. Once the model was established (after approximately 12 wk), rats were administered mosapride (1.54 mg/kg) or various doses of aqueous FAI extracts (1-4 g/kg) for 14 d. Transit function was assessed using an ink propulsion test. Rats were then sacrificed, and the ultramicrostructure of colonic tissue was examined using transmission electron microscopy. The expression of the 5-hydroxytryptamine receptor 4 (5-HTR4) and neurofilament-H was assessed in colon tissues using real-time PCR, Western blot, and immunohistochemistry.

RESULTS

Mosapride and high dose (4 g/kg) of aqueous FAI extracts significantly improved the bowel movement in cathartic colons compared to untreated model colons as measured by the intestinal transit rate (70.06 ± 7.25 and 72.02 ± 8.74, respectively, vs 64.12 ± 5.19; P < 0.05 for both). Compared to controls, the ultramicrostructure of cathartic colons showed signs of neural degeneration. Treatment with mosapride and aqueous FAI extracts resulted in recovery of ultrastructural pathology. Treatment with mosapride alone upregulated the gene and protein expression of 5-HTR4 compared to untreated controls (P < 0.05 for both). Treatment with aqueous FAI extracts (≥ 2 g/kg) increased 5-HTR4 mRNA levels (P < 0.05), but no change in protein level was observed by Western blot or immunohistochemistry. The mRNA and protein levels of neurofilament-H were significantly increased with mosapride and ≥ 2 g/kg aqueous FAI extracts compared to controls (P < 0.05 for all).

CONCLUSION

Aqueous FAI extracts and mosapride strengthen bowel movement in cathartic colons via increasing the expression of 5-HTR4 and neurofilament-H.

Effects of 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists on gastrointestinal motor activity in dogs

AIM: To study the effects of 5-hydroxytryptamine (5-HT) receptor antagonists on normal colonic motor activity in conscious dogs.

METHODS: Colonic motor activity was recorded using a strain gauge force transducer in 5 dogs before and after 5-HT2B, 5-HT3 and 5-HT4 receptor antagonist administration. The force transducers were implanted on the serosal surfaces of the gastric antrum, terminal ileum, ileocecal sphincter and colon. Test materials or vehicle alone was administered as an intravenous bolus injection during a quiescent period of the whole colon in the interdigestive state. The effects of these receptor antagonists on normal gastrointestinal motor activity were analyzed.

RESULTS: 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists had no contractile effect on the fasting canine terminal ileum. The 5-HT3 and 5-HT4 receptor antagonists inhibited phase III of the interdigestive motor complex of the antrum and significantly inhibited colonic motor activity. In the proximal colon, the inhibitory effect was dose dependent. Dose dependency, however, was not observed in the distal colon. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity.

CONCLUSION: The 5-HT3 and 5-HT4 receptor antagonists inhibited normal colonic motor activity. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity.

Efficacy of mosapride citrate with polyethylene glycol solution for colonoscopy preparation

AIM: To evaluate the efficacy and safety of adjunctive mosapride citrate for bowel preparation before colonoscopy.

METHODS: We conducted a randomized, double-blind, placebo-controlled study with mosapride in addition to polyethylene glycol (PEG)-electrolyte solution. Of 250 patients undergoing colonoscopy, 124 were randomized to receive 2 L PEG plus 15 mg of mosapride citrate (mosapride group), and 126 received 2 L PEG plus placebo (placebo group). Patients completed a questionnaire reporting the acceptability and tolerability of the bowel preparation process. The efficacy of bowel preparation was assessed by colonoscopists using a 5-point scale based on Aronchick’s criteria. The primary end point was optimal bowel preparation rates (scores of excellent/good/fair vs poor/inadequate).

RESULTS: A total of 249 patients were included in the analysis. In the mosapride group, optimal bowel preparation rates were significantly higher in the left colon compared with the placebo group (78.2% vs 65.6%, P < 0.05), but not in the right colon (76.5% vs 66.4%, P = 0.08). After excluding patients with severe constipation, there was a significant difference in bowel preparation in both the left and right colon (82.4% vs 66.7%, 80.8% vs 67.5%, P < 0.05, P < 0.01). The incidence of adverse events was similar in both groups. Among the subgroup who had previous colonoscopy experience, a significantly higher number of patients in the mosapride group felt that the current preparation was easier compared with patients in the placebo group (34/72 patients vs 24/74 patients, P < 0.05).

CONCLUSION: Mosapride citrate may be an effective and safe adjunct to PEG-electrolyte solution that leads to improved quality of bowel preparation, especially in patients without severe constipation.

Bladder, bowel, and sexual dysfunction in Parkinson's disease

Bladder dysfunction (urinary urgency/frequency), bowel dysfunction (constipation), and sexual dysfunction (erectile dysfunction) (also called “pelvic organ” dysfunctions) are common nonmotor disorders in Parkinson's disease (PD). In contrast to motor disorders, pelvic organ autonomic dysfunctions are often nonresponsive to levodopa treatment. The brain pathology causing the bladder dysfunction (appearance of overactivity) involves an altered dopamine-basal ganglia circuit, which normally suppresses the micturition reflex. By contrast, peripheral myenteric pathology causing slowed colonic transit (loss of rectal contractions) and central pathology causing weak strain and paradoxical anal sphincter contraction on defecation (PSD, also called as anismus) are responsible for the bowel dysfunction. In addition, hypothalamic dysfunction is mostly responsible for the sexual dysfunction (decrease in libido and erection) in PD, via altered dopamine-oxytocin pathways, which normally promote libido and erection. The pathophysiology of the pelvic organ dysfunction in PD differs from that in multiple system atrophy; therefore, it might aid in differential diagnosis. Anticholinergic agents are used to treat bladder dysfunction in PD, although these drugs should be used with caution particularly in elderly patients who have cognitive decline. Dietary fibers, laxatives, and “prokinetic” drugs such as serotonergic agonists are used to treat bowel dysfunction in PD. Phosphodiesterase inhibitors are used to treat sexual dysfunction in PD. These treatments might be beneficial in maximizing the patients' quality of life.

Mosapride citrate improves postoperative ileus of patients with colectomy

BACKGROUND AND AIMS

Postoperative ileus is a transient bowel dysmotility that occurs following many types of operations and is a common complication of gastrointestinal surgery. Mosapride citrate is an agonist of the 5-hydroxytryptamine 4 receptor and accelerates upper gut motility. No study has evaluated its effect on gastrointestinal motility after surgery. The aim of this study was to investigate whether mosapride citrate reduces the duration of postoperative ileus.

METHODS

Thirty patients with colon cancer who underwent colectomy were divided into two groups: the mosapride group and the control group. The mosapride group received mosapride 15 mg by mouth with a minimal amount of water three times a day, starting on postoperative day 1. The control group received only a minimal amount of water on the same schedule. Patients were allowed to resume oral feeding on postoperative day 4. Postoperative time to first flatus and defecation were evaluated, and the amount of food intake was observed. Gastrointestinal motility was recorded on postoperative day 8.

RESULTS

The appearance ratio of interdigestive migrating contractions and the motility index at the antrum and duodenum were significantly higher in the mosapride group than in the control group. The time to first flatus and defecation were significantly shorter in the mosapride group than in the control group. The amount of food intake on postoperative days 6 and 7 was significantly larger in the mosapride group than in the control group.

CONCLUSION

Mosapride citrate reduces the duration of postoperative ileus and may improve outcomes after gastrointestinal surgery.

Effect of 5-HT4 receptor agonist mosapride citrate on rectosigmoid sensorimotor function in patients with irritable bowel syndrome

BACKGROUND

The 5-HT(4) receptor agonist, mosapride citrate, accelerates gastric emptying. However, the effect of mosapride on colonic function has not been well investigated. We examined whether mosapride changes rectosigmoid motility and perception in patients with irritable bowel syndrome (IBS).

METHODS

Thirty-seven patients with IBS and 18 healthy subjects were studied. All subjects underwent a rectosigmoid barostat test to measure pain perception to intraluminal distention and resting smooth muscle motility for 20 min in the fasting state. Irritable bowel syndrome patients were then randomly assigned to receive either mosapride 15 mg (n=19) or placebo (n=18) orally with 200 mL water. Rectosigmoid motility and perception were measured again for 60 min following dosing. Rectosigmoid tone and contractility were evaluated in each 10-min period.

KEY RESULTS

The pain threshold in the patients was significantly lower than that in controls (P<0.01). There were no differences between mosapride and placebo groups in pain threshold, barostat bag volume, or number of contractions at baseline. Mosapride significantly decreased the mean bag volume (P<0.01; group × period interaction by two-way anova) and increased the mean number of contractions (P<0.05) compared with placebo, but did not affect the perception. In IBS patients with constipation (i.e., excluding diarrhea-predominant subjects), mosapride (n=13) increased rectosigmoid tone (P<0.01) and contractions (P<0.05) more than placebo (n=14).

CONCLUSIONS & INFERENCES

Mosapride stimulates colonic motility without any adverse effect. These findings suggest that mosapride may have the potential to treat IBS patients with constipation and/or functional constipation. Further clinical trials are warranted to confirm the efficacy of this agent.

The Pharmacology of TD-8954, a Potent and Selective 5-HT(4) Receptor Agonist with Gastrointestinal Prokinetic Properties

This study evaluated the in vitro and in vivo pharmacological properties of TD-8954, a potent and selective 5-HT(4) receptor agonist. TD-8954 had high affinity (pK(i) = 9.4) for human recombinant 5-HT(4(c)) (h5-HT(4(c))) receptors, and selectivity (>2,000-fold) over all other 5-hydroxytryptamine (5-HT) receptors and non-5-HT receptors, ion channels, enzymes and transporters tested (n = 78). TD-8954 produced an elevation of cAMP in HEK-293 cells expressing the h5-HT(4(c)) receptor (pEC(50) = 9.3), and contracted the guinea pig colonic longitudinal muscle/myenteric plexus preparation (pEC(50) = 8.6). TD-8954 had moderate intrinsic activity in the in vitro assays. In conscious guinea pigs, subcutaneous administration of TD-8954 (0.03-3 mg/kg) increased the colonic transit of carmine red dye, reducing the time taken for its excretion. Following intraduodenal dosing to anesthetized rats, TD-8954 (0.03-10 mg/kg) evoked a dose-dependent relaxation of the esophagus. Following oral administration to conscious dogs, TD-8954 (10 and 30 μg/kg) produced an increase in contractility of the antrum, duodenum, and jejunum. In a single ascending oral dose study in healthy human subjects, TD-8954 (0.1-20 mg) increased bowel movement frequency and reduced the time to first stool. It is concluded that TD-8954 is a potent and selective 5-HT(4) receptor agonist in vitro, with robust in vivo stimulatory activity in the gastrointestinal (GI) tract of guinea pigs, rats, dogs, and humans. TD-8954 may have clinical utility in patients with disorders of reduced GI motility.

Effects of mosapride citrate, a 5-HT4-receptor agonist, on gastric distension-induced visceromotor response in conscious rats

Mosapride citrate (mosapride), a prokinetic agent with 5-HT(4)-receptor agonistic activity, is known to enhance gastric emptying and alleviate symptoms in patients with functional dyspepsia (FD). As hyperalgesia and delayed gastric emptying play an important role in the pathogenesis of FD, we used in this study balloon gastric distension to enable abdominal muscle contractions and characterized the visceromotor response (VMR) to such distension in conscious rats. We also investigated the effects of mosapride on gastric distension-induced VMR in the same model. Mosapride (3-10 mg/kg, p.o.) dose-dependently inhibited gastric distension-induced VMR in rats. However, itopride even at 100 mg/kg failed to inhibit gastric distension-induced VMR in rats. Additionally, a major metabolite M1 of mosapride, which possesses 5-HT(3)-receptor antagonistic activity, inhibited gastric distension-induced VMR. The inhibitory effect of mosapride on gastric distension-induced visceral pain was partially, but significantly inhibited by SB-207266, a selective 5-HT(4)-receptor antagonist. This study shows that mosapride inhibits gastric distension-induced VMR in conscious rats. The inhibitory effect of mosapride is mediated via activation of 5-HT(4) receptors and blockage of 5-HT(3) receptors by a mosapride metabolite. This finding indicates that mosapride may be useful in alleviating FD-associated gastrointestinal symptoms via increase in pain threshold.

Emerging pharmacological therapies for the irritable bowel syndrome

The irritable bowel syndrome (IBS) is a symptom-based disorder defined by the presence of abdominal pain and altered bowel habits. Clinical presentations of IBS are diverse, with some patients reporting diarrhea, some constipation, and others a mixture of both. Like the varied clinical phenotypes, the pathogenesis of IBS is also diverse. IBS is not a single disease entity, but rather likely consists of several different disease states. This fact has important implications for the choices and efficacy of IBS treatment. This article reviews the IBS drugs that have reached phase II or III clinical trials.

Investigational agents for the irritable bowel syndrome

IMPORTANCE OF THE FIELD

Irritable bowel syndrome (IBS) is a common disorder with significant health and economic consequences. The etiology of IBS is complex and appears to be multifactorial. Traditional IBS therapies have been directed primarily at the relief of individual symptoms but have been largely disappointing. This has triggered the search for newer treatment strategies with improved patient outcomes.

AREAS COVERED IN THIS REVIEW

Enhanced knowledge about the putative pathophysiology of IBS has allowed the identification of new mechanistic targets for treatment. Our aim is to review emerging and promising drugs in the treatment of IBS based on disease pathophysiology. Data were extracted using Medline and PubMed search engines until January 2010. Abstracts were identified through 'Web of Science' and abstract supplements of major gastrointestinal scientific meetings. Drugs were classified according to mechanism of action and those with efficacy in trials involving human subjects examined.

WHAT THE READER WILL GAIN

Additional insight into the pathophysiology as well as current and prospective treatments of IBS.

TAKE HOME MESSAGE

A multitude of putative drug targets have been identified and some novel treatments have progressed through to human clinical trials, but very few will be approved for the market in the near future. Moreover, and in keeping with the complex and multifactorial nature of this syndrome, it is unlikely that there will be one dominant and universally effective form of therapy for all IBS patients.

The effect of mosapride citrate on constipation in patients with diabetes

OBJECTIVE

Constipation is one of the most common gastrointestinal complications suspected to degrade the quality of life in diabetic patients. Mosapride citrate is a novel selective 5-HT4 receptor agonist, which enhances gastric emptying and motility in the upper gastrointestinal tract facilitating acetylcholine release from the enteric cholinergic neurons. Since the receptors of 5-HT4 have been recently found in the lower intestine including the rectum in humans, we tested if mosapride improves constipation in diabetic patients.

PATIENTS AND METHODS

Diabetic patients with constipation were treated with mosapride citrate (15 mg/day, n=20) or domperidone (30 mg/day, n=12) as controls for 8 weeks. Bowel frequency was monitored and gastrointestinal symptoms were evaluated by Gastrointestinal Symptoms Rating Scale (GSRS).

RESULTS

Administration of mosapride resulted in increased bowel frequency after 4 and 8 weeks of administration, while no change was seen in the control group. Mosapride increased bowel frequency in even patients with diabetic polyneuropathy. Mosapride improved reflux and constipation evaluated by GSRS. As previously reported, glycemic control also improved by mosapride in these patients.

CONCLUSIONS

Administration of mosapride increased bowel frequency and ameliorated symptoms of reflux and constipation possibly stimulating the lower intestine. Given that mosapride has those beneficial aspects, it may be a useful prokinetic agent in treating diabetic patients with constipation.

Effect of mosapride citrate hydrate on the colon cleansing action of polyethylene glycol electrolyte lavage solution (PEG-ELS) in guinea pigs

Polyethylene glycol electrolyte lavage solution (PEG-ELS) is widely used for colon cleansing prior to colonoscopy and colonic surgery. It has recently been shown that coadministration of PEG-ELS and mosapride citrate hydrate (mosapride), a selective 5-HT(4)-receptor agonist, is clinically useful for barium enema examination as it allows adequate barium coating. However, there is no report showing that mosapride has beneficial effects on colon cleansing and its underlying mechanism in experimental animals. In the present study, we investigated the effects of mosapride on colonic transit and on the colon cleansing action of PEG-ELS in guinea pigs. Mosapride (10 - 20 mg/kg, i.g.) significantly enhanced colonic transit rate in guinea pigs. Although PEG-ELS alone showed adequate colon cleansing action, excess fluid remained in the colon. Coadministration of mosapride (20 mg/kg) and PEG-ELS, regardless of mosapride timing, reduced colonic content weight (dry residue and water amount) as compared to PEG-ELS alone. These findings suggest that mosapride enhances the colon cleansing action of PEG-ELS via an increase in colonic transit in guinea pigs, that is, it reduces not only fecal residue but also excessive fluid in the colonic lumen. It is therefore believed that coadministration of mosapride and PEG-ELS can allow better visualization in barium enema examination.

5-Hydroxytryptamine4 receptor agonists and colonic motility

5-Hydroxytryptamine (5-HT) released from enterochromaffin cells regulates gastrointestinal function in either an excitatory or inhibitory manner. 5-HT(3) and 5-HT(4) receptors in the gut have been the focus of clinical studies on the management of gastrointestinal motility disorders. 5-HT stimulates intestinal propulsive reflexes through 5-HT(4) receptors. 5-HT(4) receptor agonists can stimulate upper or lower gut motility, depending on their selectivity and affinity. In the guinea pig colon, the distribution of 5-HT(4) receptors in the myenteric plexus and circular muscle layer differs between the proximal and distal regions. 5-HT stimulates intestinal motility via excitatory neurons while causing relaxation of the circular muscle via 5-HT(4) receptors. In the light of these findings on the distribution of 5-HT(4) receptors, the effects of receptor agonist compounds could vary depending on the species of experimental animal and the anatomical region studied.

Effect of mosapride on recovery of intestinal motility after hand-assisted laparoscopic colectomy for carcinoma

PURPOSE

Mosapride citrate (mosapride) is a serotonin 5-hydroxytryptamine 4 receptor agonist known to promote gastric emptying and large-intestine motility. We assessed the effect of mosapride on postoperative ileus following colon surgery.

METHODS

Forty patients with colon cancer undergoing hand-assisted laparoscopic colectomy were randomly assigned to a mosapride group or a control group. The mosapride group received 15 mg of mosapride by mouth with 50 ml of water three times a day, starting on postoperative day 1. The control group received 50 ml of water on the same schedule. Patients were allowed to resume oral feeding on the evening of postoperative day 2. Postoperative time to first bowel movement was evaluated by one investigator blinded to treatment. Postoperative gastric emptying was evaluated with the [(13)C]-acetate breath test at 24 and 48 hours after the operation.

RESULTS

Postoperative time to first bowel movement was significantly shorter in the mosapride group than in the control group (48.5 vs. 69.3 hours, P = 0.0149). The time to maximal gastric emptying rate as determined by the breath test was significantly shorter in the mosapride group than in the control group at the 48-hour time point (27.9 vs. 35.3 minutes, P = 0.0294). Postoperative hospital stay was shorter in patients receiving mosapride than in controls (6.7 vs. 8.4 days, P = 0.0398). No adverse effects were observed with mosapride.

CONCLUSIONS

Gastric emptying was improved by mosapride. The results suggested that the period of postoperative ileus following hand-assisted laparoscopic colectomy can be shortened by treatment with mosapride.

Updates on treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent gastrointestinal disorder characterized by abdominal pain and discomfort in association with altered bowel habits. It is estimated to affect 10%-15% of the Western population, and has a large impact on quality of life and (in)direct healthcare costs. IBS is a multifactorial disorder involving dysregulation within the brain-gut axis, and it is frequently associated with gastrointestinal motor and sensory dysfunction, enteric and central nervous system irregularities, neuroimmune dysregulation, and post-infectious inflammation. As with other functional medical disorders, the treatment for IBS can be challenging. Conventional therapy for those with moderate to severe symptoms is largely unsatisfactory, and the development of new and effective drugs is made difficult by the complex pathogenesis, variety of symptoms, and lack of objective clinical findings that are the hallmark of this disorder. Fortunately, research advances over the past several decades have provided insight into potential mechanisms responsible for the pathogenesis of IBS, and have led to the development of several promising pharmaceutical agents. In recent years there has been much publicity over several of these new IBS medications (alosetron and tegaserod) because of their reported association with ischemic colitis and cardiovascular disease. While these agents remain available for use under restricted prescribing programs, this highlights the need for continued development of safe and effective medication for IBS. This article provides a physiologically-based overview of recently developed and frequently employed pharmaceutical agents used to treat IBS, and discusses some non-pharmaceutical options that may be beneficial in this disorder.

The in vitro pharmacological profile of TD-5108, a selective 5-HT(4) receptor agonist with high intrinsic activity

The in vitro pharmacological profile of TD-5108, a novel, selective 5-HT(4) receptor agonist, was compared to that of clinically efficacious gastroprokinetic 5-HT(4) receptor agonists. TD-5108 produced an elevation of cyclic adenosine monophosphate in human embryonic kidney 293 cells expressing the human recombinant 5-HT(4(c)) (h5-HT(4(c))) receptor (pEC(50) = 8.3) and 5-HT(4) receptor-mediated relaxation of the rat esophagus (pEC(50) = 7.9) and contraction of the guinea pig colon (pEC(50) = 7.9). In all in vitro assays, TD-5108 was a high intrinsic activity agonist, unlike tegaserod, mosapride, and cisapride which, in the majority of test systems, had lower intrinsic activity. TD-5108 had high affinity (pK (i) = 7.7) and selectivity (> or =25-fold) for h5-HT(4(c)) receptors over other biogenic amine receptors. TD-5108 was >500-fold selective over other 5-HT receptors (including h5-HT(2B) and h5-HT(3A)) and, at 3 microM, had no effect on human ether-à-go-go-related gene K+ channels. In conclusion, TD-5108 is a selective 5-HT(4) receptor agonist in vitro. The high intrinsic activity and preferential binding of TD-5108 to 5-HT4 over other 5-HT receptors may result in an improved clinical profile for the treatment of gastrointestinal disorders of reduced motility.

The effect of mosapride citrate on proximal and distal colonic motor function in the guinea-pig in vitro

Mosapride citrate (mosapride), a substituted benzamide, is a selective 5-HT(4) receptor agonist, and is known to have prokinetic properties on the stomach. However, it is unclear whether mosapride also has a prokinetic effect on the colon. We previously found that mosapride significantly shortened colonic transit time in the guinea-pig, an animal with a distribution of colonic 5-HT(4) receptors similar to that of a human. So, we aimed to separately evaluate the effect of mosapride on proximal and distal colonic motor function in the guinea-pig. Proximal (approximately 8 cm from the ileocolic junction) and distal colon (approximately 8 cm from the anus) were removed. Both ends of the colon were connected to a chamber containing a Krebs-Henseleit solution. To measure colonic transit time, artificial faeces were inserted into the oral side of the lumen and moved towards the anal side by intraluminal perfusion via a peristaltic pump. A total of 6 cm of transit was observed and time was measured in 2 cm increments. A tissue bath study, using electrical stimulation, was performed to estimate the contractile activity of the circular musculature of the colon. Immunohistochemical staining for 5-HT(4) receptors was performed in the myenteric plexus and circular muscle in both proximal and distal colon, and the stained area was measured using a microscope and computer software. Mosapride enhanced contraction at 10(-9) to 10(-7) mol L(-1), coinciding with rapid transit both in proximal and distal colon. This pattern was more prominent in proximal colon. At the high dose (10(-6) mol L(-1)) mosapride had little or no effect on colonic contraction. This stimulatory effect was attenuated by GR113808, atropine and tetrodotoxin. In the myenteric plexus, the density of 5-HT(4) receptors was significantly greater in the proximal colon than in the distal colon, but in circular muscle the density was greater in the distal colon. Thus, mosapride accelerates transit through increased contraction in the proximal colon more than distal colon. The different distribution of neuronal and muscular 5-HT(4) receptors may support these findings. Therefore, mosapride may be a useful alternative to tegaserod and cisapride for constipation.

Bladder and bowel dysfunction in Parkinson's disease

Bladder dysfunction (urinary urgency/frequency) and bowel dysfunction (constipation) are common non-motor disorders in Parkinson's disease (PD). In contrast to motor disorder, the pelvic autonomic dysfunction is often non-responsive to levodopa treatment. Brain pathology mostly accounts for the bladder dysfunction (appearance of overactivity) via altered dopamine-basal ganglia circuit, which normally suppresses the micturition reflex. In contrast, peripheral enteric pathology mostly accounts for the bowel dysfunction (slow transit and decreased phasic contraction) via altered dopamine-enteric nervous system circuit, which normally promotes the peristaltic reflex. In addition, weak strain and paradoxical anal contraction might be the results of brain pathology. Pathophysiology of the pelvic organ dysfunction in PD differs from that in multiple system atrophy; therefore it might aid the differential diagnosis. Drugs to treat bladder dysfunction in PD include anticholinergic agents. Drugs to treat bowel dysfunction in PD include dietary fibers, peripheral dopaminergic antagonists, and selective serotonergic agonists. These treatments might be beneficial not only in maximizing patients' quality of life, but also in promoting intestinal absorption of levodopa and avoiding gastrointestinal emergency.

Enhancement of the intrinsic defecation reflex by mosapride, a 5-HT4 agonist, in chronically lumbosacral denervated guinea pigs

The defecation reflex is composed of rectal distension-evoked rectal (R-R) reflex contractions and synchronous internal anal sphincter (R-IAS) reflex relaxations in guinea pigs. These R-R and R-IAS reflexes are controlled via extrinsic sacral excitatory nerve pathway (pelvic nerves), lumbar inhibitory nerve pathways (colonic nerves) and by intrinsic cholinergic excitatory and nitrergic inhibitory nerve pathways. The effect of mosapride (a prokinetic benzamide) on the intrinsic reflexes, mediated via enteric 5-HT(4) receptors, was evaluated by measuring the mechanical activity of the rectum and IAS in anesthetized guinea pigs using an intrinsic R-R and R-IAS reflex model resulting from chronic (two to nine days) lumbosacral denervation (PITH). In this model, the myenteric plexus remains undamaged and the distribution of myenteric and intramuscular interstitial cells of Cajal is unchanged. Although R-R and R-IAS reflex patterns markedly changed, the reflex indices (reflex pressure or force curve-time integral) of both the R-R contractions and the synchronous R-IAS relaxations were unchanged. The frequency of the spontaneous R and IAS motility was also unchanged. Mosapride (0.1-1.0 mg/kg) dose-dependently increased both intrinsic R-R (maximum: 1.82) and R-IAS reflex indices (maximum: 2.76) from that of the control (1.0) 6-9 days following chronic PITH. The dose-response curve was similar to that in the intact guinea pig, and had shifted to the left from that in the guinea pig after acute PITH. A specific 5-HT(4) receptor antagonist, GR 113808 (1.0 mg/kg), decreased both reflex indices by approximately 50% and antagonized the effect of mosapride 1.0 mg/kg. This was quite different from the result in the intact guinea pig where GR 113808 (1.0 mg/kg) did not affect either of the reflex indices. The present results indicate that mosapride enhanced the intrinsic R-R and R-IAS reflexes and functionally compensated for the deprivation of extrinsic innervation. The actions of mosapride were mediated through endogenously active, intrinsic 5-HT(4) receptors which may be post-synaptically located in the myenteric plexus of the anorectum.

5-Hydroxytryptophan activates colonic myenteric neurons and propulsive motor function through 5-HT4 receptors in conscious mice

Serotonin [5-hydroxytryptamine (5-HT)] acts as a modulator of colonic motility and secretion. We characterized the action of the 5-HT precursor 5-hydroxytryptophan (5-HTP) on colonic myenteric neurons and propulsive motor activity in conscious mice. Fos immunoreactivity (IR), used as a marker of neuronal activation, was monitored in longitudinal muscle/myenteric plexus whole mount preparations of the distal colon 90 min after an intraperitoneal injection of 5-HTP. Double staining of Fos IR with peripheral choline acetyltransferase (pChAT) IR or NADPH-diaphorase activity was performed. The injection of 5-HTP (0.5, 1, 5, or 10 mg/kg ip) increased fecal pellet output and fluid content in a dose-related manner, with a peak response observed within the first 15 min postinjection. 5-HTP (0.5-10 mg/kg) dose dependently increased Fos expression in myenteric neurons, with a maximal response of 9.9 +/- 1.0 cells/ganglion [P < 0.05 vs. vehicle-treated mice (2.3 +/- 0.6 cells/ganglion)]. There was a positive correlation between Fos expression and fecal output. Of Fos-positive ganglionic cells, 40 +/- 4% were also pChAT positive and 21 +/- 5% were NADPH-diaphorase positive in response to 5-HTP, respectively. 5-HTP-induced defecation and Fos expression were completely prevented by pretreatment with the selective 5-HT4 antagonist RS-39604. These results show that 5-HTP injected peripherally increases Fos expression in different populations of cholinergic and nitrergic myenteric neurons in the distal colon and stimulates propulsive colonic motor function through 5-HT4 receptors in conscious mice. These findings suggest an important role of activation of colonic myenteric neurons in the 5-HT4 receptor-mediated colonic propulsive motor response.

Measurement of 5-HT4 receptor-mediated esophageal responses by digital sonomicrometry in the anesthetized rat

INTRODUCTION

In vitro studies have demonstrated a 5-HT4 receptor-mediated relaxation of the pre-contracted rat esophagus. However, it is unclear whether 5-HT4 receptor agonists affect resting esophageal tone in vivo. The activity of 5-HT and several well-established 5-HT4 receptor agonists (tegaserod, BIMU-8, cisapride, renzapride, and mosapride) was investigated in a novel in vivo model designed to measure esophageal relaxation using the technique of digital sonomicrometry.

METHODS

Miniature piezo-electric crystals were implanted externally in a longitudinal orientation on the distal esophagus of isoflurane-anesthetized, adult male Sprague-Dawley rats. Measurement of the time for transmission of ultrasonic pulses between the implanted crystals provided a continuous recording of inter-crystal distance and hence esophageal muscle length.

RESULTS

Following cumulative intravenous administration, 5-HT (1-100 microg/kg), tegaserod (1-1000 microg/kg), BIMU-8 (3-3000 microg/kg), renzapride (10-3000 microg/kg), cisapride (30-3000 microg/kg), and mosapride (30-10,000 microg/kg) produced a dose-dependent increase in esophageal inter-crystal distance. The mean ED50 values for tegaserod, BIMU-8, renzapride, cisapride, and mosapride were 11, 49, 51, 141, and 1825 microg/kg, respectively. Pre-treatment with the selective 5-HT4 receptor antagonist, piboserod (SB-207266; 1 mg/kg subcutaneously) significantly attenuated the effects of intravenous tegaserod (1-1000 microg/kg). Following cumulative intraduodenal administration (0.03-10 mg/kg), tegaserod and mosapride exhibited a dose-dependent increase in esophageal inter-crystal distance. The doses associated with a 10% increase in muscle length from the resting level were 2.6 and>10 mg/kg for tegaserod and mosapride, respectively.

DISCUSSION

In conclusion, dose-dependent, 5-HT4 receptor agonist-mediated increases in longitudinal muscle length in the rat esophagus were observed in vivo using the technique of digital sonomicrometry. This in vivo model of esophageal activity may prove useful in evaluating the activity of novel 5-HT4 receptor agonists.

A 5-HT4 agonist, mosapride, enhances intrinsic rectorectal and rectoanal reflexes after removal of extrinsic nerves in guinea pigs

Distension-evoked reflex of rectorectal (R-R) contractions and rectointernal anal sphincter (R-IAS) relaxations can be generated in guinea pigs through an extrinsic sacral excitatory neural pathway (pelvic nerves) as well as intrinsic cholinergic excitatory and nitrergic inhibitory pathways. The aim of the present study was to create intrinsic R-R and R-IAS reflex models by pithing (destruction of the lumbar and sacral cords; PITH) and to evaluate whether the prokinetic benzamide mosapride, a 5-HT(4) receptor agonist, enhances these reflexes. The mechanical activities of the R-R and R-IAS were recorded in the anesthetized guinea pig on days 2-9 after PITH. Although the basal rectal pressure at distension after PITH was significantly lower than control, the reflex indexes of R-R contractions and synchronous R-IAS relaxations were unchanged between days 4 and 9 after PITH. The frequency of spontaneous rectal and IAS motility were also unchanged. Immunohistochemical studies revealed that the distribution of myenteric and intramuscular interstitial cells of Cajal (ICC) were not altered after PITH. Mosapride (0.1-1.0 mg/kg iv) dose-dependently increased both intrinsic R-R (maximum: 1.82) and R-IAS reflex indexes (maximum: 2.76) from control (1.0) 6-9 days after PITH. The 5-HT(4) receptor antagonist, GR-113808 (1.0 mg/kg iv) decreased the R-R and R-IAS reflex indexes by approximately 50% and antagonized the effect of mosapride (1.0 mg/kg iv). The present results indicate that mosapride moderately enhanced intrinsic R-R and R-IAS reflexes functionally compensated after deprivation of extrinsic nerves, mediated through endogenously active intrinsic 5-HT(4) receptors.

Mosapride citrate, a novel 5-HT4 agonist and partial 5-HT3 antagonist, ameliorates constipation in parkinsonian patients

Mosapride citrate is a novel selective 5-HT4 receptor agonist. It facilitates acetylcholine release from the enteric cholinergic neurons. In contrast to cisapride, mosapride does not block K(+) channels or D2 dopaminergic receptors. The objective of this study is to perform an open study of mosapride citrate's effects on constipation, a prominent lower gastrointestinal tract disorder in parkinsonian patients. A total of 14 parkinsonian patients (7 with Parkinson's disease, 7 with multiple system atrophy; 10 men, 4 women; mean age, 67 years) with constipation (10 with bowel movement < 3 times/week; 14 with difficulty in defecation) were treated with 15 mg/day of mosapride citrate for 3 months. Pre- and posttreatment objective parameters in colonic transit time (CTT) and rectoanal videomanometry were obtained. Statistical analysis was made by Student's t test. Mosapride was well tolerated by all patients except for 1, who discontinued use of the drug because of epigastric discomfort. None had a worsening of parkinsonism or other adverse events. Thirteen patients reported subjective improvements in bowel frequency (>3 times/week, 13) and difficult defecation (13). Mosapride shortened CTT of the left colon (P < 0.01) and the total colon (P < 0.05). During rectal filling, mosapride lessened the first sensation (P < 0.05) and augmented the amplitude in phasic rectal contraction. During defecation, mosapride augmented the amplitude in rectal contraction (P < 0.05) and lessened the volume of postdefecation residuals. The present study showed for the first time that mosapride citrate augmented lower gastrointestinal tract motility, as shown in CTT and videomanometry, and thereby ameliorated constipation in parkinsonian patients without serious adverse effects.

The 5-HT4 receptor agonist, tegaserod, is a potent 5-HT2B receptor antagonist in vitro and in vivo

1 Tegaserod (Zelnorm) is a potent 5-hydroxytryptamine4 (5-HT4) receptor agonist with clinical efficacy in disorders associated with reduced gastrointestinal motility and transit. The present study investigated the interaction of tegaserod with 5-HT2 receptors, and compared its potency in this respect to its 5-HT4 receptor agonist activity. 2 Tegaserod had significant binding affinity for human recombinant 5-HT2A, 5-HT2B and 5-HT2C receptors (pKi=7.5, 8.4 and 7.0, respectively). The 5-HT2B receptor-binding affinity of tegaserod was identical to that at human recombinant 5-HT4(c) receptors (mean pKi=8.4) in human embryonic kidney-293 (HEK-293) cells stably transfected with the human 5-HT4(c) receptor. 3 Tegaserod (0.1-3 microm) inhibited 5-HT-mediated contraction of the rat isolated stomach fundus potently (pA2=8.3), consistent with 5-HT(2B) receptor antagonist activity. Tegaserod produced, with similar potency, an elevation of adenosine 3',5' cyclic monophosphate in HEK-293 cells stably transfected with the human 5-HT4(c) receptor (mean pEC50=8.6), as well as 5-HT4) receptor-mediated relaxation of the rat isolated oesophagus (mean pEC50=8.2) and contraction of the guinea-pig isolated colon (mean pEC50=8.3). 4 Following subcutaneous administration, tegaserod (0.3 or 1 mg kg(-1)) inhibited contractions of the stomach fundus in anaesthetized rats in response to intravenous dosing of alpha-methyl 5-HT (0.03 mg kg(-1)) and BW 723C86 (0.3 mg kg(-1)), selective 5-HT2B receptor agonists. At similar doses, tegaserod (1 and 3 mg kg(-1) subcutaneously) evoked a 5-HT4 receptor-mediated increase in colonic transit in conscious guinea-pigs. 5 The data from this study indicate that tegaserod antagonizes 5-HT2B receptors at concentrations similar to those that activate 5-HT4 receptors. It remains to be determined whether this 5-HT2B receptor antagonist activity of tegaserod contributes to its clinical profile.

A 5-HT4 agonist mosapride enhances rectorectal and rectoanal reflexes in guinea pigs

The rectal distension-evoked reflex rectal (R-R) contractions and internal anal sphincter (R-IAS) relaxations in guinea pigs were generated through the extrinsic sacral excitatory nerve pathway (pelvic nerves) and the intrinsic cholinergic excitatory and nitrergic inhibitory nerve pathways. The aim of the present study was to evaluate whether a prokinetic benzamide, mosapride, enhances the R-R and R-IAS reflexes mediated via 5-HT4 receptors in the guinea pig. The mechanical activities of the R and IAS were recorded with a balloon connected to a pressure transducer and a strain gauge force transducer in the anesthetized guinea pig with intact spinal-intestinal pathways. Gradual and sustained rectal distension evoked R-R contractions and synchronous R-IAS relaxations. Mosapride (0.1-1.0 mg/kg i.v.) dose-dependently enhanced both R-R and R-IAS reflex responses. Reflex indexes for R-R and R-IAS maximally increased from 1.0 (control) to 1.92 and 1.88, respectively. A specific 5-HT4 receptor antagonist, GR 113808 (1.0 mg/kg i.v.), antagonized the enhancement of the R-R and R-IAS reflexes induced by mosapride 1.0 mg/kg i.v. The present results indicate that mosapride enhanced the R-R and R-IAS reflexes mediated through 5-HT4 receptors.