[Mechanism of the stimulating effect of sucrose in the small intestine as affected by morphine].

In anesthetized cats, effects of intraluminal administration of sucrose solution on potentials of the smooth muscles of the middle small intestine and discharges in afferent fibers of mesenteric nerves, were studied after morphine (1 or 10 mg/kg) administration. Morphine increased the fast potential frequency in the intestinal longitudinal muscle and the firing rate in mesenteric nerves. This was further increased after intraluminal administration of sucrose. The magnitude of the activating effect depended on the dosage and time after morphine administration. Since morphine blocks principal neurotransmitter systems but increases the serotonin release, the findings appear to support an earlier hypothesis that the activating effect of sucrose on the intestine is due to the release of serotonin by mucosal enterochromaffin cells.