Cholecystokinin (CCK) is a neuropeptide hormone and neurotransmitter widely distributed throughout the gastrointestinal (GI) tract and the central nervous system (CNS). CCK, gastrin, secretin and vasoactive intestinal peptide (VIP) belong to the gastrin/cholcystokinin family. hormone family. CCK has a biologically active C-terminal pentapeptide. CCK exists as a larger precursor hormone, preproCCK (114 amino acids), from which several smaller fragments are derived, sharing a C-terminal tetrapeptide and a sulfated tyrosine residue. Sulfated CCK (26-33) amide (CCK-8) is the major and the most potent CCK form in the brain and periphery. CCK is widely distributed in several brain regions, including the cerebral cortex, hippocampus, amygdala nuclei, and the hypothalamus. In the periphery, CCK is localized mainly in nerve fibers in the myenteric and submucosal ganglia, as well as in endocrine cells of the gastrointestinal tract.
Cholecystokinin (CCK) stimulates enzyme secretion from the pancreas, gall bladder contraction, and intestinal motility and it inhibits gastrin-induced acid secretion. CCK may be involved in several physiological and behavioral functions such as satiety, anxiety, memory processes, and analgesia and in disorders such as panic disorder. In the central nervous system (CNS), CCK acts as a neurotransmitter and modulates the action of other neurotransmitters such as dopamine, 5-hydroxytryptamine (5-HT), γ-Aminobutyric acid (GABA) and excitatory amino acids. The multiple biological actions of CCK are mediated by two classes of receptors, the peripheral/brain CCK-A receptors and the brain CCK-B receptors.
