IN-VITRO CONTRACTILE RESPONSES TO ACETYLCHOLINE IN JEJUNAL AND COLONIC TISSUE FROM STRESSED RATS

In order to investigate the mechanism for stress-induced sensitization of colonic motility responses in vivo, rats were exposed to a 15-minu te session of repeated foot shocks, and contractile responses of proxi mal jejunal and colonic strips to non-cumulative doses of acetylcholin e measured in vitro 14 days or 28 days later. No differences in dose-r esponse relationships were found between intestinal strips from foot s hocked rats and controls. Responses to the highest dose (10(-4) M) of acetylcholine in the absence and presence of tetrodotoxin did not diff er for any of the three experimental groups. Changes in cholinergic se nsitivity in the gut are unlikely to underlie the increased colonic mo tility response to stress previously reported after a single foot shoc k experience.