Motilin is a digestive hormone in the dog.

In the fasting dog, plasma motilin levels fluctuate with the various phases of the interdigestive migrating complex. In this study, we present data supporting the hormonal status of motilin in the dog, as inducer of the phase III of the interdigestive migrating motor complex. Our argument is based on the following points: (a) synthetic canine motilin (200 ng/kg i.v.) reproducing physiological plasma increases of radioimmunoassayable motilin elicited, in the duodenum, activity fronts migrating aborally and absolutely similar to the phase III of the interdigestive migrating motor complex; (b) immunoneutralization of endogenous motilin by a specific motilin antiserum (7921) eliminated the occurrence of activity fronts in the proximal intestine. Migrating phase IIIs initiated below the ligament of Treitz were still documented, supporting again the existence of a motilin-independent mechanism inducing these fronts, which we have called "ectopic." We therefore believe that motilin can be considered a (inter)digestive hormone in the dog, having the physiological role of controlling the induction of the phase III of the interdigestive migrating complex in the proximal gut.