cholecystokinin, which is produced in the small intestine, inhibits gastric secretions in the stomach.

Cholecystokinin (CCK), produced in the small intestine (mainly by I cells in the duodenum and jejunum), indeed inhibits gastric secretions in the stomach. It is released in response to the presence of fats and proteins in the digestive tract. CCK inhibits gastric acid secretion partly through stimulating the release of gastric somatostatin, which inhibits acid secretion, and it also delays gastric emptying by relaxing the proximal stomach. Additionally, CCK stimulates pancreatic enzyme secretion and bile release to aid digestion. In summary, CCK acts as an inhibitor of gastric acid secretion and gastric emptying, thereby regulating the gastric secretions and motility in response to food entering the small intestine.