Cholinergic control mechanisms for immunoreactive motilin release and motility in the canine duodenum

The relationship of immunoreactive (IR) motilin release from the duodenum to duodenal motility changes was investigated in anaesthetized dogs. Stimulation of one or both vagi at 5 or 15 Hz or field stimulation of intrinsic duodenal nerves produced Significant increases in duodenal vein IR motilin concentrations and accompanying increases in duodenal motility. However, only stimulation of both vagi at 15 Hz produced significant changes in peripheral venous concentrations of IR motilin. These occurred after a delay at a time when both the duodenum and the antrum were quiescent. Either hexamelhonium or atropine blocked IR motilin release induced by stimulation of intrinsic or extrinsic nerves while only atropine inhibited the release induced by intraarterial carbachol. The response stimulated by carbachol and blocked by atropine was tetroclotoxin insensitive and the muscarinic receptor involved was presumably located on a nonneural structure. The site sensitive to hexamethonium was presumably the neural path...