Control of lower-esophageal-sphincter contractile activity by motilin in conscious dogs.

The effect of synthetic motilin on contractile activity in the lower esophageal sphincter (LES) and the stomach has been studied in 5 healthy dogs by means of chronically implanted strain gage force transducers. Motilin produced strong contractions in the LES and the stomach simultaneously after intravenous doses ranging from 0.3 to 2.7 microgram/kg hr, which were similar to the naturally occurring interdigestive contractions in the LES and the stomach. However, these contractions could be induced only in the interdigestive state; infusion of motilin into dogs in the digestive state brought about no significant effect on either the LES or the stomach. Motilin-induced contractions in the LES and the stomach were instantly abolished by ingestion of food. It is considered that the contractions induced by motilin are identical with the naturally occurring interdigestive contractions in the LES and these contractions are the most orad component of the interdigestive cyclic recurring caudad-moving bands of strong contractions in the dogs.