Changes of excitatory and inhibitory neurotransmitters in the colon of rats underwent to the wrap partial restraint stress.

BACKGROUND: Animal models proposed to reproduce some of the human irritable bowel syndrome (IBS) symptoms are based on the hypothesis that psychosocial stressors play a pivotal role in the IBS etio-pathology. We investigated the wrap restraint stress (WRS) model with the aim to analyze the morphological changes of the entire colonic wall of these animals that showed some of the human IBS symptoms such as visceral hypersensitivity. METHODS: Male Wistar rats were used and WRS was maintained for 2 h. Abdominal contractions (AC) were recorded in the colon-rectum by balloon distension. Fecal pellets were quantitated. Colonic specimens were examined by routine histology, immunohistochemistry and western blot. KEY RESULTS: WRS animals were characterized by: (i) increase in AC number and fecal pellets mean weight; (ii) clusters of mononucleated cells, increase in eosinophilic granulocytes and mast cells in the mucosa; (iii) increase in CGRP-immunoreactive (IR) nerve fibers in the lamina propria; (iv) decrease in myenteric NK1r-IR and nNOS-IR neurons and in submucous nNOS-IR neurons; (v) decrease in SP-IR nerve fibers in the muscle wall; (vi) reduction in S100β-IR glia in the entire colonic wall; (vii) increase in CRF1r-IR myenteric neurons; (viii) no change in ChAT-IR neurons, smooth muscle cells and interstitial cells of Cajal. CONCLUSIONS AND INFERENCES: The present results support the consistency of the WRS as a potential model where part of the human IBS signs and symptoms are reproduced. The changes in glial cells and in excitatory and inhibitory neurotransmitters might represent the substrate for the dysmotility and hypersensitivity.