Cholinergic regulation of motilin release from isolated canine intestinal cells

An in vitro model was developed to study the regulation of motilin release from its endocrine-producing cell. Enzymatically dispersed cells from canine duodenojejunal mucosa were separated by centrifugal counterflow elutriation to enrich motilin content. From the motilin-enriched cell preparation, the release of motilin was determined under stimulation with various agents. Carbachol dose-dependently stimulated the release of motilin from its producing cell. Bombesin, morphine, and erythromycin, recognized stimulants for motilin release in vivo, failed to influence the secretion of motilin in vitro. Serotonin, GIP, CCK, pentagastrin, cisapride, neosynephrine, isoproterenol, or muscimol were also ineffective in the in vitro model. The response to carbachol was abolished by atropine but was not affected by somatostatin, serotonin, secretin, CCK, or GIP. These results suggest that muscarinic receptors are present on the motilin cell membrane and that acetylcholine is a major regulator of motilin release.