ENDOGENOUS CCK IS NOT INVOLVED IN THE REGULATION OF INTERDIGESTIVE GASTROINTESTINAL AND GALLBLADDER MOTILITY IN CONSCIOUS DOGS

In this study, we assessed whether endogenous CCK is involved in the regulation of interdigestive gastrointestinal and gallbladder motility in conscious dogs with force transducers chronically implanted in the gastric antrum, duodenum, jejunum and gallbladder. L364718 at a dose of 1.0 mg/kg was used as a specific and potent CCK receptor blocker, and its effect on spontaneous interdigestive motility and plasma motilin release were examined. Additionally, the contractile activity of exogenous synthetic canine motilin (20-100 ng/kg) with or without pretreatment with L364718 at a dose of 1.0 mg/kg was assessed. Whether the blocking effect of L364718 on CCK receptors was sufficient or not was verified by giving CCK-OP at a bolus dose of 10 ng/kg. As a result, cyclic changes in interdigestive motor activity and the plasma motilin concentration were not affected by pretreatment with L364718. L364718 also did not affect motilin-induced interdigestive contractile activity in the gastrointestinal tract and gallbladder. On the other hand, the effect of CCK-OP was completely abolished by pretreatment with L364718. It is concluded that endogenous CCK is not involved in the regulation of spontaneous and motilin-induced interdigestive contractions in the canine gastrointestinal tract and gallbladder.