Moxibustion ameliorates visceral hypersensitivity by regulating hypothalamus-spinal cord-colon axis in rats with irritable bowel syndrome with diarrhea.

Objectives: To observe the effect of moxibustion intervention on the hypothalamus-spinal cord-colon axis of rats with irritable bowel syndrome with diarrhea (IBS-D) and explore the mechanism of moxibustion in improving visceral hypersensitivity in rats with IBS-D.

Methods: A total of 36 SD rats were randomly divided into normal, model, and moxibustion groups, with 12 rats in each group. The IBS-D model was established by maternal separation + acetic acid stimulation + chronic restraint. Rats of the moxibustion group received bilateral moxibustion on "Tianshu" (ST25) and "Shangjuxu" (ST37) for 15 min, once a day for 7 consecutive days. The body weight, loose stool rate, and minimum threshold volume of abdominal withdrawal reflex (AWR) were measured before and after moxibustion intervention, respectively. The histopathological changes in the colon tissue were observed after HE staining. The number of colonic mucosal mast cells (MCs) was measured by toluidine blue staining. The activation of MCs was determined by tryptase positive expression level and examined by immunohistochemical staining. The content, protein and mRNA expression levels and positive expression levels of corticotropin releasing factor (CRF), substance P (SP), and calcitonin gene-related peptide (CGRP) in the hypothalamus, spinal cord and colon tissues were measured by ELISA, Western blot, real-time fluorescent quantitative PCR and immunofluorescence staining, respectively.

Results: Compared with the normal group, the loose stool rate was increased (<0.01)；the body weight and minimum threshold volume of AWR were decreased (<0.01)；the inflammatory infiltration of colon tissues was obvious；the number of MCs and positive expression level of tryptase in the colon tissue were increased (<0.01)；the contents, positive expression le-vels, protein and mRNA expression levels of CRF, SP and CGRP in the hypothalamus, spinal cord and colon tissues were increased (<0.01, <0.05) in the model group. After the intervention, compared with the model group, all these indicators showed opposite trends (<0.01, <0.05) in the moxibustion group.

Conclusions: Moxibustion can improve visceral hypersensitivity in rats with IBS-D, and its mechanism may be related to regulating the hypothalamic-spinal-colon axis to reduce the release of CRF, SP and CGRP, and thus to inhibite MC in colon tissue.