Serotonergic modulating drugs for functional gastrointestinal diseases

Gastroparesis syndromes: emerging drug targets and potential therapeutic opportunities

INTRODUCTION

Gastroparesis (Gp) and related disorders such as chronic unexplained nausea and vomiting and functional dyspepsia, known as gastropareis syndromes (GpS), have large unmet needs. Mainstays of GpS treatments are diet and drugs.

AREAS COVERED

The purpose of this review is to explore potential new medications and other therapies for gastroparesis. Before discussing possible new drugs, the currently used drugs are discussed. These include dopamine receptor antagonists, 5-hydroxytryptamine receptor agonists and antagonists, neurokinin-1 receptor antagonists and other anti-emetics. The article also considers future drugs that may be used for Gp, based on currently known pathophysiology.

EXPERT OPINION

Gaps in knowledge about the pathophysiology of gastroparesis and related syndromes are critical to developing therapeutic agents that will be successful. Recent major developments in the gastroparesis arena are related to microscopic anatomy, cellular function, and pathophysiology. The major challenges moving forward will be to develop the genetic and biochemical correlates of these major developments in gastroparesis research.

Ameliorative effect and mechanism of Si-Ni-San on chronic stress-induced diarrhea-irritable bowel syndrome in rats

Background: Chronic stress-induced diarrhea is a common clinical condition, characterized by an abnormal bowel movement and loose stools, which lacks effective treatment in the clinic. Si-Ni-San (SNS) is a compound traditional Chinese medicine extensively used in China for stress-related diarrhea. However, the mechanism is unclear.

Methods: Male Wistar rats (200 ± 20 g) were placed in a restraint cylinder and fixed horizontally for 3 h once daily for 21 consecutive days to establish a chronic restraint stress (CRS) rat model. SNS (0.6944 g/kg or 1.3888 g/kg) was given by gavage 1 h before the restraint once daily for 21 consecutive days. We examined the fecal score, dopamine β hydroxylase (DβH), and c-fos expression in locus coeruleus, norepinephrine (NE) content in ileum and plasma, expression of α1 adrenergic receptors, MLCK, MLC, and p-MLC in the colon and mesenteric arteries, contraction of isolated mesenteric arteries, The expression of subunit δ of ATP synthase (ATP5D) in intestinal tissues, ATP, ADP, and AMP content in the ileum and colon, occludin expression between ileum epithelial cells, the number of enterochromaffin cells (ECs) and mast cells (MCs) in the ileum, and 5-hydroxytryptamine (5-HT) content in the ileum and plasma.

Results: After SNS treatment, the fecal score was improved. The increased expression of DβH and c-fos in locus coeruleus was inhibited. SNS suppressed the increased NE content in the ileum and plasma, down-regulated α1 adrenergic receptors in mesenteric arteries and MLCK, MLC, p-MLC in the colon and mesenteric arteries, and inhibited the contraction of mesenteric arteries. SNS also increased the ATP content in the ileum and colon, inhibited low expression of ATP5D in intestinal tissues, inhibited the decrease of ATP/ADP in the ileum and ATP/AMP in the colon, and up-regulated the occludin expression between ileum epithelial cells. In addition, SNS inhibited the increase of ECs and MCs in the ileum and the increase of 5-HT content in the ileum and plasma.

Conclusion: This study demonstrated that SNS could improve CRS-induced abnormal feces in rats. This effect was related to the inhibition of CRS-induced increased expression of DβH and c-fos in the locus coeruleus, NE content in the ileum and plasma, and the contraction of isolated mesenteric arteries; inhibition of energy metabolism abnormality and decreased occludin expression; inhibition of increased ECs and MCs in the ileum, and 5-HT content in the ileum and plasma.

Effect of Excessive Serotonin on Pharmacokinetics of Cephalexin after Oral Administration: Studies with Serotonin-Excessive Model Rats

PURPOSE

Serotonin (5-HT) is important for gastrointestinal functions, but its role in drug absorption remains to be clarified. Therefore, the pharmacokinetics and oral absorption of cephalexin (CEX) were examined under 5-HT-excessive condition to understand the role of 5-HT.

METHODS

5-HT-excessive rats were prepared by multiple intraperitoneal dosing of 5-HT and clorgyline, an inhibitor for 5-HT metabolism, and utilized to examine the pharmacokinetics, absorption behavior and the intestinal permeability for CEX.

RESULTS

Higher levels of 5-HT in brain, plasma and small intestines were recognized in 5-HT-excessive rats, where the oral bioavailability of CEX was significantly enhanced. The intestinal mucosal transport via passive diffusion of CEX was significantly increased, while its transport via PEPT1 was markedly decreased specifically in the jejunal segment, which was supported by the decrease in PEPT1 expression on brush border membrane (BBM) of intestinal epithelial cells. Since no change in antipyrine permeability and significant increase in FITC dextran-4 permeability were observed in 5-HT-excessive rats, the enhanced permeability for CEX would be attributed to the opening of tight junction, which was supported by the significant decrease in transmucosal electrical resistance. In 5-HT-excessive rats, furthermore, total body clearance of CEX tended to be larger and the decrease in PEPT2 expression on BBM in kidneys was suggested to be one of the reasons for it.

CONCLUSIONS

5-HT-excessive condition enhanced the oral bioavailability of CEX in rats, which would be attributed to the enhanced permeability across the intestinal mucosa via passive diffusion through the paracellular route even though the transport via PEPT1 was decreased.

GASTRIC RESIDUAL VOLUME FACTORS AFTER BOWEL PREPARATION WITH MANNITOL EXPRESS

BACKGROUND

Bowel preparation with mannitol is a well-established method in Brazil. However, factors that interfere with the gastric emptying time period are yet to be known. Knowing these factors may favor the examination scheduling logistics and the individualized orientation for each patient.

OBJECTIVE

Know the factors that can contribute to the gastric emptying time after intestinal preparation with express mannitol.

METHODS

This is a prospective observational study to know factors that may contribute on the gastric emptying timing: predominant type of diet, comorbidities, medication usage, previous surgeries, number of evacuation per week, bearer of bowel obstipation, fecal type, diet type, number of evacuations after the home usage of bisacodyl before the ingestion of mannitol and number of evacuations after the ingestion of mannitol until reaching a proper bowel preparation. Before starting the colonoscopy exam, an upper digestive endoscopy exam was made to aspirate the gastric content.

RESULTS

Sample was composed of 103 patients, 55 (53.4%) women, medium age 61 (±12.1) years, medium weight 75.3 (±14.1) kg, medium height 1.7 (±10) m and medium BMI of 26.6 (±3.9) kg/m2. Average gastric residual volume was 120.9 (0-900) mL. Gastric residual volume (GRV) below 100 mL (GRV ≤100 mL) occurred in 45 (43.6%) patients, 24 (53.3%) women, medium age of 61.0 years and medium BMI of 26.7 kg/m2. Gastric residual volume above 100 mL (GRV >100 mL) occurred on 58 (56.3%) patients, 29 (50%) women, medium age of 61.0 years and medium BMI of 26.2 kg/m2. Comparing both groups, average fasting time period after the ingestion of mannitol was significantly higher on the group with GRV ≤100 mL than group with GRV >100 mL, 123.1 (60-246) vs 95.3 (55-195) minutes, respectively. There was also statistical significance concerning the usage of ezetimibe 6 (13.7%) in the group with GRV ≤100 mL and statistical significance in the group with GRV >100 mL concerning the usage of paroxetine 3 (6.7%) and tadalafil 3 (6.7%) and surgical history of prostatectomy 3 (6.7%) and bridle withdrawal 3 (6.7%).

CONCLUSION

We may conclude in this study that the usage of ezetimibe and fasting above 2 hours after the ingestion of mannitol decrease significantly the incidence of a GRV >100 mL. The usage of paroxetine, tadalafil and surgical history of prostatectomy or bridle withdrawal may contribute to increase de incidence of a GRV >100 mL.

The 5-HT3 Receptor Affects Rotavirus-Induced Motility

Rotavirus infection is highly prevalent in children, and the most severe effects are diarrhea and vomiting. It is well accepted that the enteric nervous system (ENS) is activated and plays an important role, but knowledge of how rotavirus activates nerves within ENS and to the vomiting center is lacking. Serotonin is released during rotavirus infection, and antagonists to the serotonin receptor subtype 3 (5-HT₃ receptor) can attenuate rotavirus-induced diarrhea. In this study, we used a 5-HT₃ receptor knockout (KO) mouse model to investigate the role of this receptor in rotavirus-induced diarrhea, motility, electrolyte secretion, inflammatory response, and vomiting reflex. The number of diarrhea days (P = 0.03) and the number of mice with diarrhea were lower in infected 5-HT₃ receptor KO than wild-type pups. In vivo investigation of fluorescein isothiocyanate (FITC)-dextran transit time showed that intestinal motility was lower in the infected 5-HT₃ receptor KO compared to wild-type mice (P = 0.0023). Ex vivo Ussing chamber measurements of potential difference across the intestinal epithelia showed no significant difference in electrolyte secretion between the two groups. Immediate early gene cFos expression level showed no difference in activation of the vomiting center in the brain. Cytokine analysis of the intestine indicated a low effect of inflammatory response in rotavirus-infected mice lacking the 5-HT₃ receptor. Our findings indicate that the 5-HT₃ receptor is involved in rotavirus-induced diarrhea via its effect on intestinal motility and that the vagus nerve signaling to the vomiting center occurs also in the absence of the 5-HT₃ receptor. IMPORTANCE The mechanisms underlying rotavirus-induced diarrhea and vomiting are not yet fully understood. To better understand rotavirus pathophysiology, characterization of nerve signaling within the ENS and through vagal efferent nerves to the brain, which have been shown to be of great importance to the disease, is necessary. Serotonin (5-HT), a mediator of both diarrhea and vomiting, has been shown to be released from enterochromaffin cells in response to rotavirus infection and the rotavirus enterotoxin NSP4. Here, we investigated the role of the serotonin receptor 5-HT₃, which is known to be involved in the nerve signals that regulate gut motility, intestinal secretion, and signal transduction through the vagus nerve to the brain. We show that the 5-HT₃ receptor is involved in rotavirus-induced diarrhea by promoting intestinal motility. The findings shed light on new treatment possibilities for rotavirus diarrhea.

Ondansetron treatment reduces rotavirus symptoms-A randomized double-blinded placebo-controlled trial

Background

Rotavirus and norovirus cause acute gastroenteritis with severe diarrhoea and vomiting, symptoms that may lead to severe dehydration and death. The objective of this randomized double-blinded placebo-controlled study was to investigate whether ondansetron, a serotonin receptor antagonist could attenuate rotavirus- and norovirus-induced vomiting and diarrhoea, which would facilitate oral rehydration and possibly accelerate recovery and reduce need for hospitalization.

Methods

Children with acute gastroenteritis, aged 6 months to 16 years where enrolled (n = 104) and randomized to one single oral dose (0.15mg/kg) of ondansetron (n = 52) or placebo (n = 52). The number of diarrhoea and vomiting episodes during the 24 hours following treatment was reported as well as the number of days with symptoms. Pathogens in faeces were diagnosed by real-time PCR. Outcome parameters were analyzed for rotavirus- and norovirus-positive children.

Results

One dose of oral ondansetron reduced duration of rotavirus clinical symptoms (p = 0.014), with a median of two days. Furthermore, ondansetron reduced diarrhea episodes, most pronounced in children that had been sick for more than 3 days before treatment (p = 0.028).

Conclusion

Ondansetron may be a beneficial treatment for children with rotavirus gastroenteritis.

Trial registration

European Clinical Trial Database EudraCT 2011-005700-15.

Functional Disorders: Slow-Transit Constipation

Constipation is a very common complaint, with slow-transit constipation (STC) accounting for a significant proportion of cases. Old age, female gender, psychiatric illness, and history of sexual abuse are all associated with STC. The exact cause of STC remains elusive; however, multiple immune and cellular changes have been demonstrated. Diagnosis requires evidence of slowed colonic transit which may be achieved via numerous modalities. While a variety of medical therapies exist, these are often met with limited success and a minority of patients ultimately require operative intervention. When evaluating a patient with STC, it is important to determine the presence of concomitant obstructed defecation or other forms of enteric dysmotility, as this may affect treatment decisions. Although a variety of surgical procedures have been reported, subtotal colectomy with ileorectal anastomosis is the most commonly performed and well-studied procedure, with the best track record of success.

Modulation of esophageal afferent pathways by 5-HT3 receptor inhibition

BACKGROUND

The study aims were to investigate whether neural pathways involving 5-HT3 receptors mediate: (i) distension-induced upper esophageal sphincter (UES) relaxation reflex, (ii) esophageal sensitivity to acid and electrical stimuli, and (iii) viserosomatic sensitization following acid exposure.

METHODS

In Study I, in a double-blind crossover trial (n = 9) esophageal sensory and pain thresholds to electrical stimulation were measured in the esophagus, midsternum, and the foot, before subjects were randomized to receive either Ondansetron (8 mg i.v.) or NaCl (0.9% w/v). HCl (0.15 mol L(-1)) was then infused into distal esophagus and electrical thresholds were reassessed. Following electrical sensory threshold testing, subjects received a second esophageal infusion of HCl to evaluate esophageal sensitivity to acid. In Study II (N = 10), frequencies of distension-induced UES relaxation responses were scored before and after treatment with Ondansetron and NaCl in a double-blind crossover trial.

KEY RESULTS

In Study I, ondansetron had no effect on esophageal sensitivity to HCl or acid-induced sensitization. However, blockade of 5-HT3 receptors did reduce midsternum somatic pain thresholds. Sixty minutes after esophageal acid exposure, pain thresholds were significantly lower in the ondansetron arm (mean Δ-1.36 ± 0.4 mA) when compared with NaCl (mean Δ-0.14 ± 0.58 mA) (P < 0.05). In Study II, 5-HT3 receptor blockade had no significant effect on UES relaxation reflex.

CONCLUSIONS & INFERENCES

This study does not support the hypothesis that in health, 5-HT3 receptors play a significant role in esophago-UES distention-induced relaxation reflex and esophageal sensitivity to acid or electrical stimulation. It does provide new evidence for involvement of 5-HT3 receptors in viscerosomatic sensitization.

Neurogenic and myogenic properties of pan-colonic motor patterns and their spatiotemporal organization in rats

Background and Aims

Better understanding of intrinsic control mechanisms of colonic motility will lead to better treatment options for colonic dysmotility. The aim was to investigate neurogenic and myogenic control mechanisms underlying pan-colonic motor patterns.

Methods

Analysis of in vitro video recordings of whole rat colon motility was used to explore motor patterns and their spatiotemporal organizations and to identify mechanisms of neurogenic and myogenic control using pharmacological tools.

Results

Study of the pan-colonic spatiotemporal organization of motor patterns revealed: fluid-induced or spontaneous rhythmic propulsive long distance contractions (LDCs, 0.4–1.5/min, involving the whole colon), rhythmic propulsive motor complexes (RPMCs) (0.8–2.5/min, dominant in distal colon), ripples (10–14/min, dominant in proximal colon), segmentation and retrograde contractions (0.1–0.8/min, prominent in distal and mid colon). Spontaneous rhythmic LDCs were the dominant pattern, blocked by tetrodotoxin, lidocaine or blockers of cholinergic, nitrergic or serotonergic pathways. Change from propulsion to segmentation and distal retrograde contractions was most prominent after blocking 5-HT₃ receptors. In the presence of all neural blockers, bethanechol consistently evoked rhythmic LDC-like propulsive contractions in the same frequency range as the LDCs, indicating the existence of myogenic mechanisms of initiation and propulsion.

Conclusions

Neurogenic and myogenic control systems orchestrate distinct and variable motor patterns at different regions of the pan-colon. Cholinergic, nitrergic and serotonergic pathways are essential for rhythmic LDCs to develop. Rhythmic motor patterns in presence of neural blockade indicate the involvement of myogenic control systems and suggest a role for the networks of interstitial cells of Cajal as pacemakers.

Long-term efficacy and safety of ramosetron in the treatment of diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional disease with persisting gastrointestinal symptoms that has been classified into four subtypes. Serotonin (5-hydroxytryptamine [5-HT]) plays important physiological roles in the contraction and relaxation of smooth muscle. Intraluminal distension of the intestine is known to stimulate the release of endogenous 5-HT from enterochromaffin cells, activating 5-HT3 receptors located on primary afferent neurons and leading to increases in intestinal secretions and peristaltic activity. Ramosetron, a potent and selective 5-HT3-receptor antagonist, has been in development for use in patients suffering from diarrhea-predominant IBS. In a double-blind, placebo-controlled, parallel-group study of 418 patients with diarrhea-predominant IBS-D, once-daily 5 μg and 10 μg doses of ramosetron increased the monthly responder rates of IBS symptoms compared to placebo. In a 12-week randomized controlled trial of 539 patients, a positive response to treatment was reported by 47% of a once-daily 5 μg dose of ramosetron-treated individuals compared to 27% of patients receiving placebo (P<0.001). Furthermore, the responder rate was increased in the oral administration of 5 μg of ramosetron for at least 28 weeks (up to 52 weeks), and long-term efficacy for overall improvement of IBS symptoms was also demonstrated. The rate was further increased subsequently. Adverse events were reported by 7% in ramosetron treatment. No serious adverse events, eg, severe constipation or ischemic colitis, were reported for long-term treatment with ramosetron. In conclusion, further studies to evaluate the long-term efficacy and safety of ramosetron are warranted in the form of randomized controlled trials.

Methionine enhances the contractile activity of human colon circular smooth muscle in vitro

Effective drug to manage constipation has been unsatisfactory. We sought to determine whether methionine has effect on the human colon. Human colon tissues were obtained from the specimens of colon resection. Microelectrode recording was performed and contractile activity of muscle strips and the propagation of the contractions in the colon segment were measured. At 10 µM, methionine depolarized the resting membrane potential (RMP) of circular muscle (CM) cells. In the CM strip, methionine increased the amplitude and area under the curve (AUC) of contractions. In the whole segment of colon, methionine increased the amplitude and AUC of the high amplitude contractions in the CM. These effects on contraction were maximal at 10 µM and were not observed in longitudinal muscles in both the strip and the colon segment. Methionine reversed the effects of pretreatment with sodium nitroprusside, tetrodotoxin and N(w)-oxide-L-arginine, resulting in depolarization of the RMP, and increased amplitude and AUC of contractions in the muscle strip. Methionine treatment affected the wave pattern of the colon segment by evoking small sized amplitude contractions superimposed on preexisting wave patterns. Our results indicate that a compound mimicking methionine may provide prokinetic functions in the human colon.

Chronic stress-induced alterations in mouse colonic 5-HT and defecation responses are strain dependent

Mood disorders and chronic stress are frequently associated with gastrointestinal (GI) symptoms including diarrhoea or constipation. Locally produced serotonin [5-hydroxytryptamine (5-HT)] regulates GI motility and is a key factor in the pathophysiology of stress-associated GI disorders. We aimed to establish whether chronic stress can differentially affect faecal output and colon 5-HT concentration in two inbred mouse strains: BALB/c and C57BL/6 which differ in their ability to cope with stress. Adult male BALB/c and C57BL/6 mice were restrained for 2 h daily for 10 days. Defecation was monitored during each stress session. Twenty-four hours after the last session of stress, plasma corticosterone concentration was higher than control in both strains, indicative of a physiological effect of chronic stress; however, stress-induced diarrhoea was more persistent in C57BL/6 mice. Basal concentration of colon 5-HT was higher in C57BL/6 mice, and stress elicited an increase in colon 5-HT only in this strain. Finally, naïve BALB/c mice had a higher sensitivity (incidence of diarrhoea) to 5-HT (0.33 mg/kg, i.p.) than C57BL/6 mice. Our results suggest that differential defecation responses to stress may be associated with colon 5-HT concentration, which may in turn reflect the individual sensitivity to 5-HT. In addition, C57BL/6 mice emerge as a relevant model for studying GI alterations induced by chronic stress.

Treatment of IBS-D with 5-HT3 receptor antagonists vs spasmolytic agents: similar therapeutical effects from heterogeneous pharmacological targets

There is still no agreement over optimal pharmacological treatment for irritable bowel syndrome (IBS). Patients with IBS and diarrhea (IBS-D) demonstrate both visceral hypersensitivity and impaired colonic motility with increased frequency and amplitude of giant migrating contractions (GMCs) which cause mass movements, propulsion of stools and initiation of defecation. Both antispasmodics and 5-HT3 receptor antagonists can improve the symptoms and the impaired colonic motility of patients with IBS-D though through very different mechanisms. Antispasmodics act by directly relaxing the colonic smooth muscle cells or antagonizing the excitatory neuromuscular neurotransmission. In contrast, the mechanism of action of 5HT3 antagonists is much more complex and subtle as they inhibit the ascending excitatory component of the peristaltic reflex and GMCs. There are some concerns about the safety of 5HT3 antagonists in long-term treatment. Most of the studies on the treatment of IBS have followed the pharmacological strategy of looking for big clinical effects acting on a single receptor/target. We propose a pharmacologic strategy which uses different drugs for pain and dysmotility in the same patient and includes specific drugs acting on smooth muscle cells, neuromuscular transmission, synaptic transmission and intrinsic afferents. The clinical effect on IBS symptoms would be found in the sum of all these smaller effects on multiple targets.

Randomised clinical trial: the safety and efficacy of AST-120 in non-constipating irritable bowel syndrome - a double-blind, placebo-controlled study

BACKGROUND

There is a need for safe and effective treatment options for irritable bowel syndrome (IBS). AST-120 (spherical carbon adsorbent) is a non-absorbed, carbon-based adsorbent with extensive adsorbing capability for histamine, serotonin and other substances implicated in IBS pathogenesis.

AIM

To evaluate the efficacy and safety of AST-120 in non-constipating forms of IBS.

METHODS

This randomised, double-blind, placebo-controlled trial conducted in the US and Belgium enrolled 115 male and female patients fulfilling Rome III criteria for IBS; individuals with predominantly constipation symptoms were excluded. Subjects were randomised to AST-120 2 g tds or placebo for an 8-week double-blind treatment period, followed by a 2-week single-blind placebo washout and 8-week single-blind active treatment. The primary efficacy endpoint was the proportion of subjects achieving at least a 50% reduction in the number of days with abdominal pain compared with baseline.

RESULTS

At Week 4, 26.8% of subjects treated with AST-120 responded on the primary endpoint vs. 10.2% in the placebo arm (P=0.029); at Week 8 response rates were 32.1 and 25.4% respectively (NS). More AST-120 treated subjects experienced improvement in bloating and stool consistency. These benefits abated when AST-120 was replaced by placebo, and resumed once AST-120 was restarted. The frequency of adverse events with AST-120 were less than or equal to placebo.

CONCLUSIONS

AST-120 is safe and well-tolerated and reduces pain and bloating in non-constipating IBS, although beneficial effects may be limited in duration. AST-120 represents a locally acting, non-absorbed, novel treatment for IBS and warrants further studies.

Medical management of motility disorders in patients with intestinal failure: a focus on necrotizing enterocolitis, gastroschisis, and intestinal atresia

BACKGROUND

Intestinal failure (IF) is the dependence upon parenteral nutrition to maintain minimal energy requirements for growth and development. It may occur secondary to a loss of bowel length, disorders of motility, or both. Short bowel syndrome (SBS) is a malabsorptive state resulting from surgical resection, congenital defect, or diseases associated with loss of absorptive surface area. A particularly vexing problem is associated with whole bowel and/or segmental intestinal dysmotility. Motility disorders within the context of SBS and IF may relate to rapid intestinal transit secondary to loss of intestinal length, dysmotility associated with loss or poor antegrade peristalsis, or gastroparesis. Therapy may be classified into medical (prokinetic and antidiarrheal agents) and surgical to deal with the overdistended poorly motile bowel.

METHODS

We performed a systematic review of the literature pertaining to IF, SBS, and dysmotility in the pediatric population with gastroschisis, necrotizing enterocolitis, and intestinal atresia. In addition to the available treatment options, we have provided a review of the literature and a summary of the available evidence.

CONCLUSION

Despite relatively poor level of evidence regarding the application of promotility and antidiarrheal medications in patients with SBS and IF, these agents continue to be used. Herein, we provide a review of the physiology and pathophysiology of intestinal motility/dysmotility and available strategies for the use of promotility and antidiarrheal agents in patients with IF/SBS.

Neuroinflammation in inflammatory bowel disease

Inflammatory bowel disease is a chronic intestinal inflammatory condition, the pathology of which is incompletely understood. Gut inflammation causes significant changes in neurally controlled gut functions including cramping, abdominal pain, fecal urgency, and explosive diarrhea. These symptoms are caused, at least in part, by prolonged hyperexcitability of enteric neurons that can occur following the resolution of colitis. Mast, enterochromaffin and other immune cells are increased in the colonic mucosa in inflammatory bowel disease and signal the presence of inflammation to the enteric nervous system. Inflammatory mediators include 5-hydroxytryptamine and cytokines, as well as reactive oxygen species and the production of oxidative stress. This review will discuss the effects of inflammation on enteric neural activity and potential therapeutic strategies that target neuroinflammation in the enteric nervous system.

[Promotility drugs use in critical care: indications and limits?]

Enteral feeding is often limited by gastric and intestinal motility disturbances in critically ill patients, particularly in patients with shock. So, promotility agents are frequently used to improve tolerance to enteral nutrition. This review summaries the pathophysiology, presents the available pharmacological strategies, the clinical data, the counter-indications and the principal limits. The clinical data are poor. No study demonstrates a positive effect on clinical outcomes. Metoclopramide and erythromycin seems to be the more effective. Considering the risk of antibiotic resistance, the first line use of erythromycin should be avoided in favor of metoclopramide.

Effects of mosapride citrate, metoclopramide hydrochloride, lidocaine hydrochloride, and cisapride citrate on equine gastric emptying, small intestinal and caecal motility

OBJECTIVE

Although extensive work has been done to elucidate the beneficial and unfavorable effects of gastrointestinal prokinetic agents in humans, little is known on the effects of these agents in horses. In this study, we compared the effects of mosapride, metoclopramide, cisapride, and lidocaine on equine gastric emptying, jejunal and caecal motility and evaluated these agents' adverse drug reactions (ADRs).

ANIMALS

Seven healthy adult Thoroughbreds.

PROCEDURE

Mosapride 1.0mg/kg and 2.0mg/kg, metoclopramide 0.2mg/kg, and cisapride 1.0mg/kg were dissolved in 100mL distilled water for oral administration. Lidocaine 1.3mg/kg was mixed with 500 mL saline for a 30-min intravenous infusion. Oral administration of 100mL distilled water was used as control. Gastric emptying was evaluated using (13)CO(2) breath test, and jejunal and caecal motility was assessed by electrointestinography.

RESULTS

The present study demonstrates that mosapride at doses of 1.0mg/kg and 2.0mg/kg facilitates gastric emptying in horses. Improved jejunal motility was observed following administration of mosapride (1.0mg/kg and 2.0mg/kg), metoclopramide (0.2mg/kg), and cisapride (1.0mg/kg). Similarly, improved caecal motility was observed following administration of mosapride (2.0mg/kg).

CONCLUSIONS AND CLINICAL RELEVANCE

This study shows that among the prokinetic agents studied here, only mosapride (2.0mg/kg) promotes jejunal and caecal motility in horses. Considering mosapride ADRs profile, it is believed that this compound is useful in the treatment of diseases associated with decreased GI motility, including postoperative ileus.

Slow transit constipation: a review of a colonic functional disorder

Constipation is a common gastrointestinal complaint that can cause significant physical and psychosocial problems. It has been categorized as slow transit constipation, normal transit constipation, and obstructed defecation. Both the definition and pathophysiology of constipation are unclear, but attempts to describe each of the three types have been made. Slow transit constipation, a functional colonic disorder represents approximately 15 to 30% of constipated patients. The theorized etiologies are disorders of the autonomic and enteric nervous system and/or a dysfunctional neuroendocrine system. Slow transit constipation can be diagnosed with a complete history, physical exam, and a battery of specific diagnostic studies. Once the diagnosis is affirmed and medical management has failed, there are several treatment options. Biofeedback, sacral nerve stimulation, segmental colectomy, and subtotal colectomy with various anastomoses have all been used. Of those treatment options, a subtotal colectomy with ileorectal anastomosis is the most efficacious with the data to support its use.

Review article: gastrointestinal sensory and motor disturbances in inflammatory bowel disease - clinical relevance and pathophysiological mechanisms

BACKGROUND

It is well known that inflammation has a profound impact on the neuromuscular apparatus of the gastrointestinal tract during the inflammatory insult and in periods of remission, at the site of inflammation and at distance from this site. The importance of this interaction is illustrated by the higher prevalence of functional gut disorders in patients with inflammatory bowel disease.

AIMS

To document the epidemiological and clinical significance of functional alterations of gut motility and sensitivity in patients with inflammatory bowel disease and to formulate potential pathophysiological mechanisms.

RESULTS AND CONCLUSIONS

Functional gut disorders occur frequently in patients with inflammatory bowel disease, both during inflammatory episodes and in periods of remission, and have a major impact on their quality of life. The clinical manifestations of these motility and sensitivity disorders vary and are often difficult to treat, mainly because therapeutic guidelines and specific diagnostic tests to distinguish inflammatory bowel disease from functional gut disorders are lacking. Chronic bowel inflammation results in a complicated interaction between neuroendocrine serotonin-predominant cells of the mucosa, inflammatory cells (particularly mast cells) in the submucosa, the intrinsic and extrinsic innervation and the muscular apparatus including the interstitial cells of Cajal. The outcome of this interaction is a perturbation of gastrointestinal motor function, both locally and at distance from the site of inflammation and during both acute inflammation and remission.

Effect of tegaserod on recto-sigmoid tonic and phasic activity in constipation-predominant irritable bowel syndrome

OBJECTIVES

In irritable bowel syndrome (IBS), the modulation of neural pathways may be altered and we have recently shown that postprandial recto-sigmoid tone modification is impaired. On pathophysiological grounds, we do not know whether this alteration may have a role in symptom onset and, in particular, whether an effective drug, such as tegaserod, can improve this response together with symptom severity.

METHODS

Twenty-two female patients with constipation-predominant IBS (IBS-C), diagnosed according to Rome II criteria, were studied. All subjects underwent an evaluation of the presence and severity of IBS symptoms and the recto-sigmoid barostat test to measure fasting and postprandial recto-sigmoid tone and phasic contractility. They were then randomly assigned to receive either tegaserod 6 mg b.i.d (12 patients) or placebo tablets (10 patients) for 4 wk, according to a double-blind protocol. Symptom assessment and recto-sigmoid tone and contractility were re-evaluated at the end of the treatment.

RESULTS

Both symptom severity and postprandial modification of recto-sigmoid tone improved only in the tegaserod group and a significant correlation was evident between the improvement of bloating and the improvement of postprandial recto-sigmoid tone modification. No effect of tegaserod on recto-sigmoid motility index or correlation between motility index and symptom improvement was evident.

CONCLUSIONS

In IBS-C female patients, the administration of tegaserod improves symptom severity and is accompanied by an improvement of recto-sigmoid tone response to a meal.

Wood creosote prevents CRF-induced motility via 5-HT3 receptors in proximal and 5-HT4 receptors in distal colon in rats

Wood creosote has been used as an herbal medicine against acute diarrhea caused by food poisoning and has an inhibitory effect on colonic motility and enterotoxin-induced ion secretion. Since no previous studies have examined the effects of wood creosote on stress-induced alteration of colonic motility, we examined the effects on the colonic motility altered by intracerebroventricular (i.c.v.) injection of corticotropin-releasing factor (CRF), which is a key mediator in responses to stress. We recorded motor activity in proximal and distal colon of unrestrained conscious rats via two manometory catheters. The frequencies of phase III-like contraction and the % motor indices in both proximal and distal colon were measured. At the same time the number of fecal pellets excreted was counted. I.c.v. injection of CRF increased the motor activity in both proximal and distal colon, and these effects were completely antagonized by i.c.v. injection of a selective CRF type 1 antagonist but not by a CRF type 2 antagonist. Changes in colonic motility induced by CRF were reversed by intravenously administered wood creosote. Intraluminal administration of the 5-HT(3) receptor antagonist granisetron, or the 5-HT(4) receptor antagonist SB 204070 blocked the increase in colonic motility induced by i.c.v. injection of CRF. Wood creosote prevented the increase in colonic motility induced by the 5-HT(3) receptor agonist SR57227A in the proximal colon, while it prevented the increase in colonic motility induced by the 5-HT(4) receptor agonist RS67506 in the distal colon. These results indicate that wood creosote prevents the increase in colonic motility induced by CRF via 5-HT(3) receptors in the proximal colon, and via 5-HT(4) receptors in the distal colon, suggesting that wood creosote might be useful to treat stress-induced diarrhea.

Promotility medications--now and in the future

Gastrointestinal promotility drugs stimulate smooth muscle contractions to enhance gastric emptying and small and large bowel transit. Currently available drug classes with prokinetic properties include antidopaminergic agents, serotonergic agents, and motilin-receptor agonists. Due to moderate prokinetic effects, poor symptomatic responses and the presence of adverse effects, there is a clear need for new classes of prokinetics. Several newer prokinetic drugs and drug classes are currently under evaluation. Selecting candidate agents and designing the appropriate therapeutic trials is hampered by the lack of insight in the pathophysiology of motility-related symptoms. As gastrointestinal motor disorders are chronic, relapsing, and remitting disorders, it seems desirable that studies with candidate prokinetic drugs establish a long-term efficacy and not only short-term effects on gastrointestinal functions.

Role of serotonin in the pathophysiology of the irritable bowel syndrome

The irritable bowel syndrome (IBS) is a complex disorder that is associated with altered gastrointestinal motility, secretion, and sensation. Serotonin (5-HT) is an important neurotransmitter and paracrine signalling molecule in the gastrointestinal tract. 5-HT release from enterochromaffin (EC) cells initiates peristaltic, secretory, vasodilatory, vagal and nociceptive reflexes. The enteric nervous system (ENS) comprises a semiautonomous effector system that is connected to the central autonomic network. Parasympathetic and sympathetic nerves modulate the ENS via afferent and efferent communications. Ongoing, bidirectional brain-gut interactions involving 5-HT pathways occur that significantly influence the effector systems. Altered 5-HT signalling may lead to both intestinal and extraintestinal symptoms in IBS. 5-HT directly and indirectly affects intestinal motor and secretory function and abnormalities may lead to either constipation or diarrhea. 5-HT modulates sensation and perception of visceral stimulation at peripheral and central sites. Therapeutic agents targeting altered 5-HT signalling may provide new, effective treatments for patients with IBS.

Chronic idiopathic slow transit constipation: pathophysiology and management

OBJECTIVE

Patients with idiopathic slow-transit constipation comprise a small proportion of the total population complaining of constipation. The purpose of this review is to present an update of pathophysiology of this disorder and its application in clinical management.

METHODS

Medline was used to search English language articles published up to the end of September 2002 on the subject of slow-transit constipation.

RESULTS AND CONCLUSIONS

Patients with idiopathic slow-transit constipation can be divided into 2 subgroups: 1. patients with normal proximal gastrointestinal motility and with onset of constipation in connection with childbirth or pelvic surgery. This subgroup may benefit from consideration of surgical treatment; 2. patients who have a dysfunctional enteric nervous/neuroendocrine system and exhibit colonic dysmotility as part of a generalised gastrointestinal dysmotility. Surgical approach in this subgroup seems to be unhelpful and medical treatment appears to be a better approach.

The specialty of colon and rectal surgery: its impact on patient care and role in academic medicine

The specialty of colon and rectal surgery, a specialty of general surgery, has evolved from the field of proctology. Clinical care has demonstrated decreased number of patients requiring intestinal stomas, improved quality of life in patients with benign anorectal disorders, and more favorable results in patients afflicted with primary and recurrent colorectal cancer. Basic science investigations have spawned from clinical questions such as the molecular biology of colorectal cancer, use of cyclooxygenase inhibitors and polyp regression, and novel cytokine antagonists in inflammatory bowel disease. Medical students are exposed to surgeons with expertise in anorectal anatomy and physiology, mechanisms of carcinogenesis and the importance of screening for detection of colorectal cancer, and novel therapies for inflammatory bowel disease. Surgical residents benefit by having a colorectal surgeon on the faculty by repetitive exposure to anorectal surgery, low pelvic anastomoses, stoma creation and closure, and surgery involving the small intestine. Senior colorectal surgeons will develop critical pathways for the healthcare delivery of patients afflicted with colorectal disease. The specialty of colorectal surgery will continue to translate into improved patient care and positively impact in academic medicine by providing expertise into student and resident training and generate highly sophisticated clinical and basic science investigations.