RESUMO
Objective:To explore the effect of Tongxie-Yaofang on visceral sensitivity in IBS-D and the possible mechanism. Methods:Divided 30 male SD rats (one-day old) into normal group (10 rats) and IBS-D model group (20 rats) randomly. IBS-D was induced by the method of neonatal maternal separation and restraint stress. After successful modeling, the IBS-D model group was randomly divided into model group and Tongxie-Yaofang group, with 10 rats in each group. Tongxie-Yaofang group was given Tongxie-Yaofang formula, 4.92 g/ml by gavage, while the normal and model groups were given the same amount of normal saline, rats were gavaged with 2 ml/100 g body weight once a day for 14 days. The electromyography of the exorectus muscle was used to meature colorectal distension and by using electronic constant pressure apparatus to evaluate visceral sensitivity. The morphology of colon by HE staining and Enzyme-linked immunosorbent assay (ELISA) were used to determine the level of colonic 5-hydroxytryptamine (5-HT), qPCR was used to detect the colonic mRNA expression of serotonin transporter (SERT) and Western blot was used to detect SERT expression in colon and hypothalamus. Results:Compared with the model group, at the expansion pressure of 60 mmHg and 80 mmHg, the electromyographic response [(179.51 ± 18.26)% vs. (226.42 ± 25.78)%; (242.13 ± 15.42)% vs. (306.02 ± 51.51)%] in Tongxie-Yaofang group was significantly decreased ( P<0.05 or P<0.01). The colonic content of 5-HT was significantly lower than that in the model group [(8.85 ± 0.53) ng/mg vs.(12.25 ± 1.95) ng/mg] ( P<0.01), the expression of SERT mRNA (0.85 ± 0.12 vs. 0.38 ± 0.02) and SERT protein (0.53 ± 0.11 vs. 0.36 ± 0.17) in the colon was significantly increased ( P<0.05 or P<0.01), the expression of SERT protein (0.88 ± 0.12 vs. 0.36 ± 0.13) in the hypothalamus was significantly increased ( P<0.05). Conclusion:Tongxie-Yaofang could relieve the visceral hypersensitivity, which may be achieved by regulating the 5-HT and SERT expression.