五羟色胺在胃肠道功能性疾病中的研究现状

Mixed 5-HT3 antagonists/5-HT4 agonists for irritable bowel syndrome: a systematic review

AIM: To systematically review the evidence for the efficacy and safety of mixed 5-HT₃ antagonists/5-HT₄ agonists in the treatment of irritable bowel syndrome (IBS).

METHODS: According to the recommendations of the Cochrane Collaboration, a meta-analysis was conducted on 2 841 patients from eight eligible trials with respect to the usage of these drugs.

RESULTS: The unimprovement in IBS global symptoms [42.7% vs 46.9%, RR = 0.91, 95% CI (0.58, 1.43)], abdominal pain [53.2% vs 59.3%, RR = 0.90, 95% CI (0.72, 1.11)] or constipation [54.0% vs 58.5%, RR = 0.91, 95%CI (0.74, 1.12)] did not differ significantly in the presence of cisapride vs placebo. In the presence of renzapride, lower doses (1 mg/d and 2 mg/d) were found not to be superior to placebo in attenuating global symptoms [RR = 0.95, 95% CI (0.67, 1.35); RR = 0.79, 95% CI (0.67, 1.17)]; however, high dose of renzapride (4 mg/d) resulted in a significant difference [67.8 % vs 73.9%, RR = 0.91, 95% CI (0.86, 0.96)]. There was no significant difference in the incidence of adverse events among cisapride [RR = 1.52, 95% CI (0.58, 3.99)], renzapride [RR = 1.11, 95% CI (0.98, 1.24)] and placebo.

CONCLUSION: Except for high dose of renzapride (4 mg/d) which could relieve the global symptoms in IBS-C patients, there was no sufficient evidence to indicate that low dose renzapride or cisapride might be used to improve the global symptoms, abdominal pain as well as constipation discomfort.

Role of serotonin in the pathogenesis of chronic constipation

Serotonin (5-hydroxytryptamine, 5-HT) is a monoamine neurotransmitter of profound importance in the enteric nervous system. About 95% of the serotonin in the body is found in the GI tract; 90% is in enterochromaffin cells (EC cells) and the remaining 10% in enteric neurons. It plays a key role in the initiation of peristaltic and secretory reflexes and in the modulation of visceral sensations. There are many reports of serotonin in functional bowel disorders, and most of them mainly focus on irritable bowel syndrome (IBS), but serotonin in constipation is rarely reported. Chronic constipation (CC) is a commonly encountered disease, especially in elderly patients. The role of 5-HT plays in CC has been emphasized, and its effects in physiology, pathology and treatment of CC are continuously being resolved. This article is a review of the progress in understanding the role of 5-HT in the pathogenesis and treatment of chronic constipation.

Expression of 5-HT and SP in the rectum of rats during heroin abstinence, detoxification or relapse

AIM: To investigate the expression of 5-hydroxytryptamine (5-HT) and substance P (SP) in the rectum of rats during heroin abstinence, detoxication, and relapse.

METHODS: Male Sprague-Dawley rats were divided into normal control group (NCG), saline control group (SCG), and experiment group (EG). The EG group was further divided into heroin abstinence group (HAG), methadone detoxication group (MDG), and heroin relapse group (HRG). Rectum tissue samples were taken from each group to perform immunohistochemistry to detect the expression of 5-HT and SP.

RESULTS: Compared with the NCG and SCG groups, the immunostaining density of 5-HT- and SP-positive cells was greater, the numbers of 5-HT- and SP-positive cells increased (5-HT: 10 d: 5.09 ± 3.39 vs 3.16 ± 2.05, 2.80 ± 2.13; 24 d: 5.05 ± 3.04 vs 3.16 ± 2.05, 2.81 ± 1.85; SP: 10 d: 2.55 ± 1.35 vs 1.29 ± 0.86, 1.37 ± 0.93; 24 d: 2.57 ± 1.27 vs 1.29 ± 0.86, 1.39 ± 0.79, all P < 0.05), and the mean grey degree of 5-HT- and SP-positive cells decreased (F = 36.642, 4.583, P < 0.05) in the HAG and HRG groups. Compared with the NCG and SCG groups, there were no statistical significances in the immunostaining density, numbers, and mean grey degree of 5-HT- and SP- positive cells in the MDG group (all P > 0.05).

CONCLUSION: Altered expression of 5-HT and SP in the tunica mucosa recti of rats during heroin abstinence or relapse suggests that 5-HT and SP can regulate the recovery of digestive function during heroin abstinence, detoxification, and relapse.

Serotonin transporter expression in rats with chronic visceral hypersensitivity

AIM: To determine whether colonic serotonin transporter (SERT) expression is altered in rats with visceral hypersensitivity and to explore the possible mechanism underlying the pathogenesis of visceral hypersensitivity.

METHODS: A rat model of visceral hypersensitivity was created by intracolonic injection of acetic acid between postnatal days 8 and 21. The expression of SERT mRNA and protein in the colonic epithelium was detected by RT-PCR and immunohistochemistry, respectively. The levels of serotonin in plasma and colonic tissue were also measured.

RESULTS: Colon irritation in neonates resulted in chronic visceral hypersensitivity in the absence of identifiable peripheral pathology. Under different capacities the abdominal withdrawal reflex (AWR) score in rats with chronic visceral hypersensitivity was significantly higher than that in controls (P < 0.01). Although plasma serotonin content significantly increased in rats with visceral hypersensitivity compared to controls (95.75 ± 15.99 vs 72.17 ± 8.01, P < 0.01), no significant difference was noted in colonic serotonin content between the two groups. SERT immunoreactivity in colonic epithelium was significantly reduced in rats with visceral hypersensitivity (0.187 ± 0.010 vs 0.191 ± 0.011, P < 0.01), whereas a significant increase was noted in SERT mRNA level in the colon of rats with visceral hypersensitivity compared to controls (16.02 ± 3.7 vs 9.47 ± 2.34, P < 0.05).

CONCLUSION: In visceral hypersensitivity, the increase in serotonin content is mainly due to decreased degradation of the protein. The expression and function of SERT may be different in serotonergic neurons compared to colonic epithelial mucosa cells.