The influence of the novel 5-HT1A agonist R137696 on the proximal stomach function in healthy volunteers

Gastrointestinal hormones and regulation of gastric emptying

PURPOSE OF REVIEW

In this review, we evaluate recent findings related to the association between gastrointestinal hormones and regulation of gastric emptying.

RECENT FINDINGS

Motilin and ghrelin, which act during fasting, promote gastric motility, whereas most of the hormones secreted after a meal inhibit gastric motility. Serotonin has different progastric or antigastric motility effects depending on the receptor subtype. Serotonin receptor agonists have been used clinically to treat dyspepsia symptoms but other hormone receptor agonists or antagonists are still under development. Glucagon-like peptide 1 agonists, which have gastric motility and appetite-suppressing effects are used as a treatment for obesity and diabetes.

SUMMARY

Gastrointestinal hormones play an important role in the regulation of gastric motility. Various drugs have been developed to treat delayed gastric emptying by targeting gastrointestinal hormones or their receptors but few have been commercialized.

The Role of Serotonin Neurotransmission in Gastrointestinal Tract and Pharmacotherapy

5-Hydroxytryptamine (5-HT, serotonin) is a neurotransmitter in both the central nervous system and peripheral structures, acting also as a hormone in platelets. Although its concentration in the gut covers >90% of all organism resources, serotonin is mainly known as a neurotransmitter that takes part in the pathology of mental diseases. Serotonin modulates not only CNS neurons, but also pain transmission and platelet aggregation. In the periphery, 5-HT influences muscle motility in the gut, bronchi, uterus, and vessels directly and through neurons. Serotonin synthesis starts from hydroxylation of orally delivered tryptophan, followed by decarboxylation. Serotonin acts via numerous types of receptors and clinically plays a role in several neural, mental, and other chronic disorders, such as migraine, carcinoid syndrome, and some dysfunctions of the alimentary system. 5-HT acts as a paracrine hormone and growth factor. 5-HT receptors in both the brain and gut are targets for drugs modifying serotonin neurotransmission. The aim of the present article is to review the 5-HT receptors in the gastrointestinal (GI) tract to determine the role of serotonin in GI physiology and pathology, including known GI diseases and the role of serotonin in GI pharmacotherapy.

Gastric accommodation: Physiology, diagnostic modalities, clinical relevance, and therapies

BACKGROUND

Gastric accommodation is an essential gastric motor function which occurs following ingestion of a meal. Impaired gastric fundic accommodation (IFA) is associated with dyspeptic symptoms. Gastric accommodation is mediated by the vagal pathway with several important physiologic factors such as duodenal nutrient feedback playing a significant role. IFA has been described as a pathophysiologic factor in several gastrointestinal disorders including functional dyspepsia, diabetic gastropathy, post-Nissen fundoplication, postsurgical gastrectomy, and rumination syndrome. Modalities for gastric accommodation assessment include gastric barostat, intragastric meal distribution via scintigraphy, drinking tests (eg, water load), SPECT, MRI, 2D and 3D ultrasound, and intragastric high-resolution manometry. Several treatment options including sumatriptan, buspirone, tandospirone, ondansetron, and acotiamide may improve symptoms by increasing post-meal gastric volume.

PURPOSE

Our aim is to provide an overview of the physiology, diagnostic modalities, and therapies for IFA. A literature search was conducted on PubMed, Google Scholar, and other sources to identify relevant studies available until December 2020. Gastric accommodation is an important gastric motor function which if impaired, is associated with several upper gastrointestinal disorders. There are an increasing number of gastric accommodation testing modalities; however, each has facets which warrant consideration. Evidence regarding potentially effective therapies for IFA is growing.

Comparative efficacy and acceptability of psychotropic drugs for functional dyspepsia in adults: A systematic review and network meta-analysis

ABSTRACT

Psychotropic drugs are frequently used for functional dyspepsia (FD); however, the efficacy of these drugs for treating FD remains controversial. We aimed to comprehensively compare the relative efficacies of different psychotropic drugs for FD in adults.To conduct this study, we searched the PubMed, Embase, and Cochrane Library databases on March 10, 2019, and conducted a frequentist network meta-analysis on the search results. The primary outcome was treatment efficacy estimated by the proportion of patients who achieved a certain percentage decrease in symptoms or who dropped below the threshold of the global FD symptom scores. The secondary outcome was acceptability, defined as all-cause discontinuation. Odds ratios (ORs) were reported with 95% confidence intervals (CIs).We deemed 10 trials to be eligible for analysis, and these trials included 970 participants and 10 psychotropic drugs. Flupentixol + melitracen (F + M) (OR, 10.00; 95% CI, 1.59 to 62.73), tandospirone (3.24, 1.38 to 7.60), imipramine (2.21, 1.02 to 4.79), and amitriptyline (1.71, 1.06 to 3.09) were significantly superior to placebo. According to the surface under the cumulative ranking curve, the most effective treatment was F + M (89.0%), whereas the least effective was R137696 (13.6%). In terms of acceptability, escitalopram (0.32, 0.11 to 0.92) was ranked as the worst drug (12.6%), followed by imipramine and sertraline.The present network meta-analysis suggests that F + M, tandospirone, imipramine, and amitriptyline are more effective than placebo as treatment for FD. Our results indicate that among the ten psychotropic drugs included, F + M is likely to be the most effective drug for alleviating dyspepsia symptoms.

Transcutaneous electrical acustimulation synchronized with inspiration improves gastric accommodation impaired by cold stress in healthy subjects

BACKGROUND

The aim of this study was to investigate whether transcutaneous electrical acustimulation (TEA) synchronized with inspiration (STEA), a method known to enhance vagal activity, was more effective than TEA in improving cold stress-induced impairment in gastric accommodation (GA) and dyspeptic symptoms in healthy subjects.

METHODS

Each of fifteen healthy subjects was studied in five randomized sessions: control (warm nutrient liquid), cold nutrient liquid (CNL), CNL+sham-TEA, CNL+TEA, and CNL+STEA. The subjects were requested to drink Ensure until reaching maximum satiety. STEA was performed using the same parameters as TEA but asking the subjects to breathe in when they sensed each stimulation train. The electrogastrogram (EGG) and electrocardiogram (ECG) were recorded to assess gastric slow waves (GSW) and autonomic functions, respectively.

KEY RESULTS

GA was reduced with the CNL in comparison with the warm drink but increased with TEA and STEA; STEA was more potent than TEA in improving GA; STEA was more potent in improving GSW than TEA; STEA significantly increased vagal activity and decreased sympathetic activity compared with TEA.

CONCLUSIONS AND INFERENCES

TEA synchronized with inspiration is more potent than TEA in improving cold stress-induced impairment in GA and GSW and dyspeptic symptoms and might be a novel noninvasive therapy for treating stress-induced dysmotility and dyspeptic symptoms.

Dual Alpha2C/5HT1A Receptor Agonist Allyphenyline Induces Gastroprotection and Inhibits Fundic and Colonic Contractility

BACKGROUND

Allyphenyline, a novel α2-adrenoceptor (AR) ligand, has been shown to selectively activate α2C-adrenoceptors (AR) and 5HT1A receptors, but also to behave as a neutral antagonist of α2A-ARs. We exploited this unique pharmacological profile to analyze the role of α2C-ARs and 5HT1A receptors in the regulation of gastric mucosal integrity and gastrointestinal motility.

METHODS

Gastric injury was induced by acidified ethanol in Wistar rats. Mucosal catalase and superoxide dismutase levels were measured by assay kits. The effect of allyphenyline on electrical field stimulation (EFS)-induced fundic and colonic contractions was determined in C57BL/6 mice.

RESULTS

Intracerebroventricularly injected allyphenyline (3 and 15 nmol/rat) dose dependently inhibited the development of mucosal damage, which was antagonized by ARC 239 (α2B/C-AR and 5HT1A receptor antagonist), (S)-WAY 100135 (selective 5HT1A receptor antagonist), and JP-1302 (selective α2C-AR antagonist). This protection was accompanied by significant elevation of mucosal catalase and superoxide dismutase levels. Allyphenyline (10(-9)-10(-5) M) also inhibited EFS-induced fundic contractions, which was antagonized by ARC 239 and (S)-WAY 100135, but not by JP-1302. Similar inhibition was observed in the colon; however, in this case only ARC 239 reduced this effect, while neither selective inhibition of α2C-ARs and 5HT1A receptors nor genetic deletion of α2A- and α2B-ARs influenced it.

CONCLUSIONS

Activation of both central α2C-ARs and 5HT1A receptors contributes to the gastroprotective action of allyphenyline in rats. Its inhibitory effect on fundic contractions is mediated by 5HT1A receptors, but neither α2-ARs nor 5HT1A receptors take part in its inhibitory effect on colonic contractility in mice.

Ameliorating effect of transcutaneous electroacupuncture on impaired gastric accommodation induced by cold meal in healthy subjects

BACKGROUND

Impaired gastric accommodation is recognized as one of major pathophysiologies in functional dyspepsia and gastroparesis. Electroacupuncture has been shown to improve gastric accommodation in laboratory settings. It is, however, unknown whether it exerts similar ameliorating effect in humans and whether needleless transcutaneous electroacupuncture (TEA) is also effective in improving gastric accommodation.

AIM

The aim was to investigate the effects of TEA on gastric accommodation, gastric slow waves, and dyspeptic related symptoms.

METHODS

Thirteen healthy volunteers were studied in four randomized sessions: control, cold nutrient liquid, cold nutrient liquid + sham-TEA, and cold nutrient liquid + TEA. The subjects were requested to drink Ensure until reaching maximum satiety. The electrogastrogram (EGG) and electrocardiogram (ECG) were recorded to assess the gastric and autonomic functions respectively.

RESULTS

1) Gastric accommodation was reduced with the cold drink in comparison with the warm drink (P = 0.023). TEA improved the impaired gastric accommodation from 539.2 ± 133.8 ml to 731.0 ± 185.7 ml (P = 0.005). 2) The percentage of normal gastric slow waves in six subjects was significantly decreased in the cold session (P = 0.002) and improved in the TEA session (P = 0.009 vs sham; P < 0.001 vs cold). 3) TEA showed significant improvement in the bloating (80.8 ± 5.7 vs 61.2 ± 26.2, P = 0.011), postprandial fullness (48.1 ± 12.0 vs 34.2 ± 21.2, P = 0.042), and nausea (29.6 ± 10.9 vs 19.2 ± 11.2, P = 0.026) in comparison with sham-TEA session. 4) Neither cold drink nor TEA altered vagal activities (P > 0.05).

CONCLUSIONS

TEA improves impaired gastric accommodation and slow waves induced by cold drink and the effect does not seem to be mediated via the vagal mechanisms.

The effects of 5-hydroxytryptamine1a receptor agonist, buspirone on the gastric fundus accommodation in an animal model using guinea pigs

BACKGROUND

To date, few animal experiments have been conducted to examine the effects and mechanisms of buspirone in inducing the relaxation of the gastric fundus. The aim of this study is to examine the effects and mechanisms of buspirone, 5-HT(1a) receptor agonist, in the accommodation of gastric fundus muscle in an animal experimental model using guinea pigs.

METHODS

In the current study, we performed an immunohistochemistry for 5-HT(1a) receptors in the tissue samples collected from the stomach of guinea pig, an ex vivo experiment to examine the electrical field stimulation (EFS)-induced relaxation of the circular muscle in the gastric fundus in guinea pigs and an in vivo experiment to measure the intragastric pressure through the insertion of the balloon catheter in the fundus.

KEY RESULTS

Immunohistochemical stains for 5-HT(1a) receptor could confirm the expression of 5-HT(1a) receptor in guinea pig stomach. There was a significant dose-dependent inhibition of the EFS-induced relaxation of fundic muscle strips following the treatment with WAY-100635 (5-HT(1a) antagonist), but this was significantly improved following the treatment with buspirone. An in vivo measurement of the gastric fundic tone showed that there was a significant decrease in the intragastric pressure at same volume by pretreatment with buspirone as compared with the vehicle control, but this could be prevented with the treatment with WAY-100635.

CONCLUSIONS & INFERENCES

Based on our results, it can be concluded that buspirone is effective in relaxing the gastric fundus via 5-HT(1a) receptor pathway in both in vitro and in vivo experimental models using guinea pigs.

DA-9701: A New Multi-Acting Drug for the Treatment of Functional Dyspepsia

Motilitone^® (DA-9701) is a new herbal drug that was launched for the treatment of functional dyspepsia in December 2011 in Korea. The heterogeneous symptom pattern and multiple causes of functional dyspepsia have resulted in multiple drug target strategies for its treatment. DA-9701, a compound consisting of a combination of Corydalis Tuber and Pharbitidis Semen, has being developed for treatment of functional dyspepsia. It has multiple mechanisms of action such as fundus relaxation, visceral analgesia, and prokinetic effects. Furthermore, it was found to significantly enhance meal-induced gastric accommodation and increase gastric compliance in dogs. DA-9701 also showed an analgesic effect in rats with colorectal distension induced visceral hypersensitivity and an antinociceptive effect in beagle dogs with gastric distension-induced nociception. The pharmacological effects of DA-9701 also include conventional effects, such as enhanced gastric emptying and gastrointestinal transit. The safety profi le of DA-9701 is also preferable to that of other treatments.

Efficacy of buspirone, a fundus-relaxing drug, in patients with functional dyspepsia

BACKGROUND & AIMS

Impaired accommodation and hypersensitivity to gastric distention are believed to be involved in the development of functional dyspepsia (FD). Buspirone, a 5-hydroxytryptamine 1A receptor agonist, relaxes the proximal stomach in healthy individuals. We studied the effects of buspirone on symptoms and mechanisms of FD.

METHODS

We performed a randomized, double-blind, placebo-controlled, crossover study of 17 patients (13 women; mean age, 38.5 ± 2.4 years). The study included 2 treatment periods of 4 weeks each, separated by a 2-week washout period. In the first period, 7 participants were given buspirone (10 mg, 3 times daily for 4 weeks) and 10 were given placebo 15 minutes before meals; patients switched groups for the second period. We assessed meal-related symptoms and severity, along with gastric sensitivity, accommodation, and emptying (by using barostat and breath tests) before and after 4 weeks of treatment.

RESULTS

Buspirone significantly reduced the overall severity of symptoms of dyspepsia (7.5 ± 1.3 vs 11.5 ± 1.2 for placebo; P < .005) and individual symptoms of postprandial fullness, early satiation, and upper abdominal bloating, whereas placebo had no significant effect (all P < .05). Buspirone did not alter the rate of gastric emptying of solids or sensitivity to gastric distention, but it significantly increased gastric accommodation, compared with placebo (229 ± 28 vs 141 ± 32 mL, respectively; P < .05), and delayed gastric emptying of liquids (half-life = 64 ± 5 vs 119 ± 24 minutes, respectively). Adverse events were similar when patients were given buspirone or placebo.

CONCLUSIONS

In patients with FD, 4 weeks of administration of buspirone significantly improved symptoms and gastric accommodation, compared with placebo, whereas gastric emptying of liquids was delayed.

Effects of DA-9701, a novel prokinetic agent, on gastric accommodation in conscious dogs

BACKGROUND AND AIM

DA-9701, a novel prokinetic agent formulated with Pharbitis Semen and Corydalis Tuber, has strong prokinetic effects, and enhances gastric compliance in conscious dogs. In this study, the effects of DA-9701 on gastric accommodation were studied in conscious dogs.

METHODS

Beagle dogs with an implanted gastric cannula in the stomach were used in this study. After an overnight fast, the dogs received DA-9701 orally, or served as a positive control that received sumatriptan or a negative control before ingestion of a meal. The basal and postprandial gastric volumes were monitored at a constant operating pressure using an electronic barostat. To investigate the long-lasting effects on increased postprandial gastric volume, the area under the volume versus time curve (AUC) was calculated.

RESULTS

DA-9701 significantly increased the basal gastric volume compared to the negative controls (P < 0.05); the effects were comparable to sumatriptan. DA-9701 and sumatriptan significantly increased gastric accommodation compared to the negative control (P < 0.05). In the negative control, the gastric volume reached the maximal volume 40 min after the meal, and then gradually decreased. However, with DA-9701, the increased gastric volume remained significantly elevated for 60 min postprandially (P < 0.05). DA-9701 significantly increased the value of AUC compared to the negative control; this was observed during both the early and late postprandial phases (P < 0.05).

CONCLUSIONS

A novel prokinetic agent, DA-9701, improved gastric accommodation by increasing the postprandial gastric volume; these effects persisted for 60 min after a meal.

G-protein β3 subunit 825CC genotype is associated with postprandial distress syndrome with impaired gastric emptying and with the feeling of hunger in Japanese

BACKGROUND

G-protein dysfunction related alteration of intracellular signal transduction might be linked to various abnormalities of functional gastrointestinal (GI) disorders. Serotonin (5-hydroxytryptamine; 5-HT) as well as G-protein is also key signaling molecule sensorimotor functions in the GI tract. Thus, this study aims to evaluate the correlation between gastric emptying and GNβ3 and 5-HTs polymorphisms in functional dyspepsia (FD) as defined by Rome III classification.

METHODS

Seventy-four patients presenting with typical symptoms of FD (epigastric pain syndrome: EPS, n=24; postprandial distress syndrome: PDS, n = 51) and sixty-four healthy volunteers were enrolled. Gastric motility was evaluated with the T(max) value using the (13) C-acetate breath test. We used Rome III criteria to evaluate upper abdominal symptoms and SRQ-D scores to determine depression status. GNβ3-C825T, 5-HT(1A) -C1019G, 5-HT(2A) -G1438A, 5-HT(3A) -C42T, and 5-HT(4A) -G353+6A polymorphisms were analyzed in DNA from blood samples of enrolled subjects. Genotyping was performed by polymerase chain reaction.

KEY RESULTS

There was a significant relationship (P=0.045) between GNβ3 825CC genotype and PDS patients without gastro-esophageal reflux symptoms with impaired gastric emptying. In Japanese, GNβ3 825CC genotype in FD patients was significantly associated (P=0.0485) with the feeling of hunger compared with GNβ3 825CT and TT genotypes.

CONCLUSIONS & INFERENCES

  Our results suggest that the GNβ3 825CC genotype is significantly associated with PDS patients without gastro-esophageal reflux with impairments of gastric emptying and also with the feeling of hunger in patients with FD. Further studies are needed to clarify whether the GNβ3 825CC genotype is linked to disturbances of gastric emptying via altered signal transduction responses.

Serotonin transporter gene polymorphism may be associated with functional dyspepsia in a Japanese population

Background

Although familial clustering of functional dyspepsia (FD) has been reported, the role of genetics in the susceptibility to FD is still not well understood. In the present study, the association between serotonin transporter (SERT) gene (SLC6A4) polymorphism and FD was explored.

Methods

Subjects were divided into either a postprandial distress syndrome (PDS) group or an epigastric pain syndrome (EPS) group according to the Rome III criteria. The healthy controls were those who had visited a hospital for an annual health check-up. The presence of the SLC6A4 promoter polymorphism, 5-hydroxytryptamin transporter gene linked polymorphic region (5-HTTLPR), was then evaluated, and logistic regression analysis was used to test all variables.

Results

The 5-HTTLPR genotype distribution was 448 SS, 174 SL, and 24 LL in controls and 30 SS, 20 SL, and 3 LL in FD subjects. No significant correlation was found between the 5-HTTLPR genotype and FD. When the genotypes and subtypes of FD were exploratory evaluated, the SL genotype was significantly associated with PDS [odds ratio (OR) = 2.24, 95% confidence interval (CI); 1.16-4.32, P = 0.034 after Bonferroni correction] compared to the SS genotype adjusted for sex and age. Comparison of the SS genotype with the SL/LL genotype also showed a significant association of genotype with PDS (OR = 2.32, 95% CI; 1.23-4.37, P = 0.009).

Conclusion

The present results suggest that 5-HTTLPR L allele may influence the susceptibility to PDS.

Gastroduodenal motility

PURPOSE OF REVIEW

Abnormalities of gastroduodenal motility are considered key players in the pathogenesis of upper gastrointestinal symptoms in disorders such as functional dyspepsia and gastroparesis. Abnormalities of sensory control are considered another important factor that contributes to symptom generation. This review summarizes recent progress in our understanding of gastroduodenal motility and sensitivity in health and in disease.

RECENT FINDINGS

Although gastric and small intestinal motility remain an important focus of research, including the application of the SmartPill (SmartPill Corp., Buffalo, New York, USA) wireless motility monitoring capsule, duodenal sensitivity and low-grade duodenal inflammation are new areas of interest in the pathogenesis of functional dyspepsia. A number of genetic polymorphisms associated with functional dyspepsia are being investigated, but large-scale studies are still lacking. Central processing of visceral stimuli, and its role in the pathogenesis of functional dyspepsia, is another important emerging topic. Therapeutic studies have reported on novel pharmacological approaches in functional dyspepsia and gastroparesis, as well as gastric electrical stimulation in the treatment of refractory gastroparesis.

SUMMARY

There is gradual progress in our understanding of the pathogenesis of gastroduodenal symptoms. Areas of recent advances including the recognition of low-grade duodenal inflammation, the role of central nervous system processing in visceral hypersensitivity and the exploration of novel pharmacotherapeutic approaches.

Influence of Weitongxiaopi Decoction on serum and gastric ghrelin and leptin in rats with functional dyspepsia

AIM: To observe the influence of Weitongxiaopi Decoction (WTXP) on serum and gastric ghrelin and leptin in rats with functional dyspepsia of liver-depression and spleen-deficiency type.

METHODS: A rat model of functional dyspepsia was established by the improved tail clamp method. The rats with functional dyspepsia were then given WTXP or cisapride (CP) for 3 wk. After the treatment, serum and gastric ghrelin and leptin were examined by enzyme-linked immunosorbent assay (ELISA) and Western blot, respectively.

RESULTS: The content of serum ghrelin was significantly higher (132.7 ± 10.78 vs 103.17 ± 13.46, P < 0.01) and that of serum leptin was significantly lower (31.30 ± 5.81 vs 37.55 ± 4.32, P < 0.01) in the WTXP group than in the CP group. The expression level of gastric ghrelin was significantly higher (150.87 ± 12.76 vs 118.97 ± 8.93, P < 0.01) and that of gastric leptin was significantly lower (60.28 ± 9.28 vs 67.75 ± 5.67, P < 0.01) in the WTXP group than in the CP group.

CONCLUSION: Weitongxiaopi Decoction can increase the levels of serum and gastric ghrelin but decrease those of serum and gastric leptin in rats with functional dyspepsia.

Efficacy of the 5-HT1A agonist tandospirone citrate in improving symptoms of patients with functional dyspepsia: a randomized controlled trial

OBJECTIVES

Functional dyspepsia (FD) is a common condition in the general population; however, its treatment remains a challenge. The aim of this study was to examine the efficacy of tandospirone citrate, a new partial agonist of the 5-hydroxytryptamine 1A (5-HT1A) receptor, in improving the symptoms of patients with FD.

METHODS

In this double-blind, placebo-controlled, multicenter study, FD patients were randomized to treatment with 10 mg t.i.d. tandospirone citrate or to placebo for 4 weeks. The primary end point was change in abdominal symptom scores. The difference in the proportion of responders (a total abdominal symptom score of 0 or 1) was also assessed. The quality-of-life questionnaire, the SF-8, and a psychological test questionnaire, the State-Trait Anxiety Inventory (STAI), were completed at baseline and at weekly intervals.

RESULTS

Data were available for 144 patients: 73 for tandospirone and 71 for placebo. Improvements in total abdominal scores were significantly larger with tandospirone than placebo at weeks 1, 2, and 4. Significantly greater improvements in the tandospirone group were observed in upper abdominal pain (P=0.02) and discomfort (P=0.002) at week 4. The proportion of responders was significantly greater in the active treatment arm at weeks 3 (P=0.017) and 4 (P=0.0016). Significant improvements in STAI (P<0.0001) were reported in both arms, as well as in the majority of questions in the SF-8 (P=0.04). No serious adverse events were reported, with similar rates in both study arms.

CONCLUSIONS

Despite a considerable placebo effect, the benefits of tandospirone were shown in terms of improvement in abdominal symptom scores.

A placebo-controlled trial of the 5-HT1A agonist R-137696 on symptoms, visceral hypersensitivity and on impaired accommodation in functional dyspepsia

Acute studies suggested a therapeutic benefit for fundus-relaxing drugs in functional dyspepsia (FD) with visceral hypersensitivity (VH) to gastric distention or impaired accommodation (IA), but long-term studies are lacking. R-137696 is a serotonin-1A (5-HT(1A)) receptor agonist which relaxes the proximal stomach in man. Our aim was to investigate the influence of R-137696 on symptoms in FD with VH or IA. Randomized, double-blind, placebo-controlled, parallel group study of 4 weeks R-137696 2 mg t.i.d. in FD with VH or IA. Symptoms were assessed using the patient assessment of upper gastrointestinal symptom severity index (PAGI-SYM) total score and individual symptom subscales. Barostat studies were performed before and after 4 weeks of treatment. Fifty-three patients (33 VH and 20 IA), 18 men, mean age 40 +/- 13 years were recruited. Twenty-four received placebo and 29 received R-137696. In VH patients, both placebo and R-137696 improved total symptom scores, with a tendency for superiority of placebo (-1.12 vs-0.51, P = 0.07). Placebo was superior for the subscales of early satiety, bloating, fullness and discomfort (all P < 0.05). In IA, both placebo and R-137696 had no significant influence on total or individual symptom scores (-0.08 and -0.27). In VH, both placebo and R-137696 increased the discomfort volume, without a statistical difference between both arms (+120 and +164 mL). In IA, both placebo and R-137696 enhanced accommodation, without a statistical difference between both (+77 and +159 mL). Adverse events were similar for drug and placebo. A 4-week administration of the fundus-relaxing 5-HT(1A) agonist R-137696 failed to significantly improve symptoms, VH or gastric accommodation compared to placebo.

Influence of buspirone on gastric sensorimotor function in man

BACKGROUND

Previous studies have suggested involvement of 5HT(1) receptors in the control of gastric tone.

AIM

To study the effect of buspirone, a 5HT(1A) agonist, on gastric sensorimotor function in healthy volunteers.

METHODS

Ten healthy volunteers (six males and four females, ages 20-29 years) participated in a barostat study evaluating the influence of single oral doses of buspirone (5, 10, 20, 30 and 40 mg) on tone and sensitivity of the proximal stomach. In addition, the effect of placebo or the three lowest doses of buspirone on gastric emptying was assessed using a solid and liquid gastric emptying breath test.

RESULTS

Compared to preadministration volumes, buspirone increased proximal stomach volumes in a dose-dependent manner, with significant fundic relaxation after 30 and 40 mg doses (intra-balloon volume increases of respectively 258 +/- 80 mL and 273 +/- 49 mL, P < or = 0.05). Pressure thresholds during gastric distention were not altered, but corresponding intraballoon volumes were significantly increased after 30 and 40 mg doses (respective discomfort volumes 596 +/- 73 vs. 791 +/- 87 mL and 630 +/- 73 vs.741 +/- 60 mL, both P < 0.05). Buspirone significantly slowed solid and liquid gastric emptying at the 20-mg dose.

CONCLUSION

Buspirone dose-dependently relaxes the proximal stomach in the fasting state and decreases the gastric emptying rate in healthy volunteers.

Dyspepsia

PURPOSE OF REVIEW

This review critically evaluates the current status of dyspepsia and, in particular, recent advances in epidemiology, pathophysiology and management. The very definition of dyspepsia and of functional dyspepsia, in particular, continues to generate controversy; the Rome III redefinition of functional dyspepsia remains to be proven to be of clinical value. Overlap with gastroesophageal reflux and irritable bowel syndrome further complicate clinical definitions.

RECENT FINDINGS

Most studies of pathophysiology continue to focus on gastric sensory and motor functions, though some intriguing early data raise the possibility of an infective or immunological contribution. There have been few, if any, major breakthroughs in treatment; most recent studies address instead the niceties of Helicobacter pylori eradication and acid suppressive strategies.

SUMMARY

This continued lack of progress in the area can only lead one to question some very basic concepts in this disorder, such as does functional dyspepsia, as we have come to know it, really exist as a distinct entity?

The role of serotonin in irritable bowel syndrome: implications for management

Irritable bowel syndrome (IBS) is a poorly understood, common, chronic condition characterized by -abdominal discomfort associated with altered bowel habits in the absence of structural or biochemical abnormalities. Despite the significant economic and personal burden associated with IBS, treatment options remain limited. Serotonin is recognized as a key neurotransmitter in intestinal secretory, sensory, and motor function. Although the pathophysiology of IBS is incompletely understood, there is evidence that abnormalities in brain-gut signaling and serotonin metabolism play a role. This article reviews the evidence that serotonin, one of the better-understood neurotransmitters with respect to its role in human central and intestinal physiology, plays a role in IBS. Serotonin signaling is discussed, with a focus on receptor subtypes and the therapeutic agents that target these receptors. Evidence that IBS is associated with perturbations in serotonin metabolism at various steps in the signaling pathway is also addressed, along with the limitations on alteration in serotonin metabolism as the sole explanation for the constellation of symptoms observed in patients with IBS.

Serotonin pharmacology in the gastrointestinal tract: a review

Serotonin (5-hydroxytryptamine or 5-HT) plays a critical physiological role in the regulation of gastrointestinal (GI) function. 5-HT dysfunction may also be involved in the pathophysiology of a number of functional GI disorders, such as chronic constipation, irritable bowel syndrome and functional dyspepsia. This article describes the role of 5-HT in the enteric nervous system (ENS) of the mammalian GI tract and the receptors with which it interacts. Existing serotonergic therapies that have proven effective in the treatment of GI functional disorders and the potential of drugs currently in development are also highlighted. Advances in our understanding of the physiological and pathophysiological roles of 5-HT in the ENS and the identification of selective receptor ligands bodes well for the future development of more efficacious therapies for patients with functional GI disorders.

Mechanisms of serotonergic agents for treatment of gastrointestinal motility and functional bowel disorders

Most of the body's serotonin is released in the gut where it plays an important role in the control of gastrointestinal (GI) motility, sensitivity and muscle tone by activating different receptor subtypes. This review focuses on the known effects of selective serotonin reuptake inhibitor and serotonin receptor agonists and antagonists on the sensorimotor function of the GI tract and describes the therapeutic potential of these actions for GI motility and functional bowel disorders.

Serotonergic and non-serotonergic targets in the pharmacotherapy of visceral hypersensitivity

Visceral hypersensitivity is considered a key mechanism in the pathogenesis of functional gastrointestinal (GI) disorders. Targeting visceral hypersensitivity seems an attractive approach to the development of drugs for functional GI disorders. This review summarizes current knowledge on targets for the treatment of visceral hypersensitivity, and the status of current and future drug and probiotic treatment development, and the role of pharmacogenomic factors.