Comparative studies on the effects of bradykinin and vagal stimulation on motility in the stomach and colon.

The effect of bradykinin on gastric and colonic motility was studied in anaesthetized cats with volume recording devices and compared with the effects of vagal nerve stimulation. When administered intrarterially bradykinin caused a profound and prolonged gastric relaxation. Stimultaneously there was a marked and likewise prolonged colonic contraction. The gastric relaxation closely mimicked the atropine resistant relaxation elicited by vagal nerve stimulation. These effects could not be blocked by antiadrenergic drugs and it is suggested that bradykinin and the unknown transmittor substance(s) released on vagal stimulation act in a similar way on the gastric smooth muscles and that a kinin mechanism may be involved in the vagal response. As regards the colonic motor response it was shown that bradykinin does not reproduce the vagal motility effects on colon smooth muscle but mimicks closely the atropine resistant expulsive contraction elicited by activation of the pelvic nerves.