Cholecystokinin stimulates the secretion of the enzymatic component of pancreatic juice. The major stimulus for the release of Cholecystokinin is the presence of fatty acids and other lipids in the duodenum. Cholecystokinin also causes the sphincters of the pancreatic duct and hepatopancreatic ampulla to relax.
Parasympathetic stimulation through the vagus nerves also stimulates the secretion of pancreatic juices rich in pancreatic enzymes, and sympathetic impulses inhibit secretion. The effect of vagal stimulation on pancreatic juice secretion is greatest the cephalic and gastic phases of stomach secretion.