Cholecystokinin

Cholecystokinin (CCK) is a type I secretory cell in the small intestinal mucosa and is also found in the brain and peripheral nerves. It is the most powerful neurotransmitter in the central and peripheral nervous system. CCK is the most abundant peptide in the brain. . CCK functions both endocrine hormones and neurotransmitters, and is one of the well-known "brain-gut peptides". CCK exists in many molecular forms, including CCK33, which contains 33 amino acids, as well as CCK39, CCK58 and so on. Among them, CCK58 has the entire biological activity of the entire cholecystokinin molecule, and the activity is 2-10 times stronger than that of CCK33. Type Ⅰ cells mainly exist in the duodenum and upper jejunum. Excited vagus nerves, hydrochloric acid, proteins and decomposition products, fats and hydrolysates, and Ca2 + ions are factors that stimulate CCK secretion. CCK stimulates pancreatic enzymes secreted by the pancreas. Feedback inhibits CCK release. CCK has a wide range of biological activities, mainly acting as hormones and neurotransmitters. The effects of its hormonal effects on the secretory function of the digestive system are: ① stimulate pancreas to secrete pancreatin and bicarbonate, enhance pancreatic enzyme activity, and stimulate islets to release insulin. ② CCK has a common receptor on parietal cells that competes with gastrin, and can inhibit the gastric acid secretion response caused by gastrin. ③ Stimulate the duodenal secretion, and also have a certain stimulation effect on liver and bile secretion. The effects on the digestive system motor function are: ① CCK has a strong contraction of the gallbladder. ② It also has an excitatory effect on gastrointestinal smooth muscle, causing contraction of the stomach and pyloric sphincter in a resting state, and inhibiting contraction of the esophageal sphincter and Oddi's sphincter.