Comparison of Gallbladder Contractions Induced by Motilin and Cholecystokinin in Dogs

Abstract

Contractile activity in the gallbladder was measured by means of chronically implanted force transducers in conscious dogs. Intravenous infusion o f motilin (0.3–0.9 mg/kg·h) induced transient contractions during the interdigestive but not during the digestive period. The contractions of the gallbladder occurred simultaneously with the initiation of phase 2 contractions in the duodenum. The duration (5.9 ± 0.15 min) and the contractile force (11.5 ± 0.57 g) were not different from those with three doses o f motilin. The motilin-induced contractions, however, started with dose-related periods of latency and terminated before the cessation of motilin infusion. In contrast, cholecystokinin-octapeptide (0.03–0.09 μg/kg·h) induced dose-dependent tonic contractions (7.8 ± 0.41 g to 17.7 ± 0.77 g) not only during the interdigestive period but also during the digestive period. These contractions also started with dose-related periods of latency and lasted the duration of the infusion. Atropine sulfate (0.025 mg/kg) inhibited both motilin and cholecystokinin—octapeptide-induced contractions of the gallbladder. The present study reveals that motilin has a stimulus effect on the gallbladder only during the interdigestive period and that motilin-induced contractions were different from those induced by cholecystokinin—octapeptide, a common stimulator of the gallbladder.