[Moxibustion relieves abdominal hypersensitivity and diarrhea by regulating colonic 5-hydroxytryptamine signaling pathway in rats with diarrhea type irritable bowel syndrome]

Objective: To observe the effect of moxibustion on visceral pain, diarrhea, colonic 5-hydroxytryptamine (5-HT) content, and expression of tryptophan hydroxylase 1 (TPH1), serotonin reup take transporter (SERT) and 5-hydroxytryptamine receptor 3 (5-HT3R) in colon tissue of rats with diarrhea irritable bowel syndrome (IBS-D), so as to reveal its underlying mechanisms in treating IBS-D.

Methods: Thirty male SD rats were randomly divided into blank control, model and moxibustion groups (n＝10 rats in each group). The IBS-D model was established by chronic restraint combined with gavage of Senna leaf solution. Moxibustion was applied to bilateral "Tianshu" (ST25) and "Shangjuxu" (ST37) for 30 min, once a day for 7 days. After the treatment, the loose stool rate (number of loose stool/total number of feces granules X100%) and the minimum volume threshold of abdominal reflex (abdominal pain threshold) induced by rectal dilatation were observed. The content of colonic 5-HT was detected by using ELISA, and the expression of TPH1, SERT and 5-HT3R mRNAs and proteins were detected by using quantitative real time-PCR and Western blot, respectively.

Results: Compared with the blank control group, the minimum volume threshold of abdominal retraction reflex and the relative expression of SERT protein and mRNA were significantly decreased (P<0.01), and the loose stool rate, colonic 5-HT content, and relative expression of TPH1 and 5-HT3R proteins and mRNAs were notably increased in the model group (P<0.01). After moxibustion, both the decrease of minimum volume threshold and SERT protein and mRNA expressions and the increase of loose stool rate, colonic 5-HT content and TPH1 and 5-HT3R protein and mRNA expressions were reversed (P<0.01).

Conclusion: Moxibustion of ST25 and ST37 can relieve abdominal hypersensitivity and diarrhea in IBS-D model rats, which is related to its effects in down-regulating colonic 5-HT content and expression of TPH1 and 5-HT3R proteins and mRNAs and in up-regulating expression of SERT protein and mRNA (regulating 5-HT/5-HT3R signaling)．.

Keywords: 5-hydroxytryptamine signaling pathway; Colonic tissue; Diarrhea; Diarrhea-type irritable bowel syndrome; Moxibustion; Visceral hypersensitivity.