Motilin and a synthetic enkephalin induce colonic motor complexes (CMC) in the conscious dog

In the conscious dog migrating and nonmigrating colonic motor complexes (CMC) were recorded by means of chronically implanted strain gauge force transducers. Intravenous injection of a synthetic enkephalin analogue immediately induced a premature CMC at all three recording sites of the colon. Naloxone inhibited the enkephalin- but not motilin-induced CMC. We therefore exclude that motilin acts by release of endogenous enkephalins. The two peptides stimulate CMC in the canine colon by different pathways. Naloxone alone had no effect on normal colonic motility, suggesting strongly that endogenous enkephalins do not modulate regular CMC in the dog.