Therapeutic Effect of Donglingcao Tablet on Post-inflammatory Irritable Bowel Syndrome in Rats

OBJECTIVE To investigate the therapeutic effect and the underlying mechanism of Donglingcao tablet on post-inflammatory irritable bowel syndrome (PI-IBS) in rats induced by trinitrobenzene sulfonic acid(TNBS). METHODS PI-IBS rat model was established by TNBS solution intra-colonic administration. PI-IBS rats were orally administered with Donglingcao tablet at the dose of 0.4, 0.8 and 1.2 g·kg^-1·d^-1 for consecutive 2 weeks. After drugs treatment, visceral pain threshold pressure was measured by abdominal withdrawal reflex test; colon transit was evaluated by water avoidance stress, colonic enterochromaffin cell number was investigated by immunohistochemistry, serotonin content was determined by LC-MS/MS method, and the protein expression of tryptophan hydroxylase (TPH) was tested by Western Blot technique. RESULTS Compared with the normal rats, PI-IBS rats presented reduced visceral pain threshold pressure, increased faecal pellet output, as well as elevated enterochromaffin cell density, serotonin content and TPH expression (P<0.05). Compared with PI-IBS rats, high and median dose of Donglingcao tablet treatment significantly increased the pain threshold pressure, markedly reduced the faecal pellet output, and the colonic enterochromaffin cell density as well as serotonin content and TPH expression were all decreased (P<0.05). CONCLUSION The analgesic effect and therapeutic effect on colon dysfunction of Donglingcao tablet is associated with the reduced enterochromaffin cell hyperplasia and serotonin content in the colon of PI-IBS rats.