THE INTESTINAL INHIBITORY RESPONSE TO OXYTOCIN, VASOPRESSIN AND BRADYKININ

¹ Department of General Pharmacology, Biological Research Division, Schering Corporation, Bloomfield, New Jersey

Evidence has been presented which indicates that each of the three polypeptides, oxytocin, vasopressin and bradykinin, produces a prompt inhibition of intestinal motility in the anesthetized dog. In the case of oxytocin and vasopressin, this smooth muscle inhibitory response is also reflected in the isolated guinea-pig ileum, the isolated guinea-pig tracheal chain and the rabbit ileum. Bradykinin produces a stimulant effect on these isolated smooth muscle preparations. In the anesthetized dog, the intestinal inhibitory responses to the three polypeptides are not reduced by adrenergic blockade, in the form of Dibenamine and dichloroisoproterenol; ganglionic blockade, in the form of chlorisondamine; or adrenergic neurone blockade, in the form of guanethidine or bretylium. Diphenhydramine and atropine both reduce the intestinal inhibitory responses to the three polypeptides without reducing the intestinal inhibitory responses to epinephrine or papaverine. The blocking action of diphenhydramine or atropine is probably not mediated through their antihistaminic or anticholinergic actions, respectively. However, this blocking effect is shared by other antihistamine drugs, such as tripelennamine and chlorpheniramine, and other anticholinergics, such as propantheline.