Cholecystokinin inhibits gastric emptying by acting on both proximal stomach and pylorus.

Cholecystokinin is a potent inhibitor of gastric emptying. It is known to both relax the proximal stomach and contract the pyloric sphincter, and either one or both of these actions could mediate inhibition of gastric emptying. We investigated the relative importance of these two actions by studying the effectiveness of the C-terminal octapeptide of cholecystokinin (OP-CCK) to inhibit the emptying of a liquid meal (300 ml saline) before and after operations that either remove or destroy the pyloric mechanism (antrectomy and pyloroplasty), or lead to loss of accommodation of the proximal stomach (vagotomy), and after both vagotomy and antrectomy, and vagotomy and pyloroplasty. The results show that OP-CCK causes dose-related inhibition of gastric emptying in the intact dog. After either pyloroplasty or antrectomy the effectiveness of low but not of high doses of OP-CCK is lost. After vagotomy, OP-CCK at any dose was ineffective. The findings suggest that cholecystokinin inhibits gastric emptying by acting both on the pylorus and on the proximal stomach.