Ovarian hormone modulates 5-hydroxytryptamine 3 receptors mRNA expression in rat colon with restraint stress-induced bowel dysfunction

AIM: To examine the effects of ovarian hormone on the expression of 5-hydroxytryptamine 3 receptors (5-HT3R) in rat colon of restraint stress-induced bowel dysfunction. METHODS: Twenty-four female Sprague-Dawley rats were randomly divided into three groups of 8 each: sham operation, ovariectomy (OVX) and ovariectomy with estrogen (E2) and progesterone (P) replacement therapy (OVX+E2+P). The rats were subjected to 1-h restraint stress 4 wk after operation. The changes of defecation were monitored by collection of fecal pellets. The gonadal steroids were measured in duplicate by radioimmunoassay (RIA). The expression of 5-HT3R mRNA in the colon was studied by RT-PCR. RESULTS: Compared with sham group and OVX+E2+P group, OVX group showed increase in fecal pellets and decrease in the time of vitreous pellets excretion (P<0.01). Serum levels of E2 and P were suppressed in OVX group and restored following treatment with ovarian steroids (P<0.01), and the levels of 5-HT3R mRNA in the colon of ovariectomized rats were significantly increased, the expression of 5-HT3R mRNA was significantly decreased in hormone replacement therapy group (P<0.01). CONCLUSION: Ovarian hormone plays a role in the regulation of 5-HT3R expressions in restraint stress-induced bowel dysfunction of rats. The interactions between ovarian steroids and gastrointestinal tract may have major pathophysiological implications in 5-HT-related disorders, such as irritable bowel syndrome (IBS).