The effect of chronic variable stress on bowel habit and adrenal function in rats.

Background and Aim:  Increased colonic motility is a well-known stress response and corticotropin releasing hormone plays an important role in this response, but sequential change of bowel habit and adrenal function during chronic stress has not been reported. The objective of this study was to evaluate the effect of chronic stress on bowel habit and adrenal function. Methods:  Male Sprague-Dawley rats were exposed to chronic variable stress (CVS) for 6 weeks. We measured daily the number and weight of pellets and weekly urinary corticosterone. After 6 weeks of experiment, visceromotor response (VMR) to colorectal distention (CRD), serum corticosterone and adrenal glands weight were measured. Results:  The number and weight of pellets in CVS rats was greater than those of the control rats initially and decreased during the later period. However, CVS rats showed continuously exaggerated daily variation of pellet number than control rats to the end of experimental period. Urinary corticosterone was increased in CVS rat until the fifth week, but urine and serum corticosterone were not statistically different between groups at the sixth week. However, the relative weight of adrenal glands was higher in CVS rats at the sixth week. CVS rats showed exaggerated VMR to CRD than the control rats. Conclusions:  The prolonged and variable stress to rats induced sustained bowel habit dysfunction and visceral hypersensitivity without adaptation. Chronic stress also increased adrenal activity from the early phase and finally caused adrenal hypertrophy with relatively decreased activity. But adrenal change was not parallel to bowel habit change and it remains to be seen whether adrenal dysfunction is directly related to bowel habit dysfunction.