Cholecystokinin receptors are a group of G-protein coupled receptors which bind the peptide hormones cholecystokinin (CCK) and gastrin. Two types of functional membrane receptors, cholecystokinin A receptor (CCK-AR), located mainly on pancreatic acinar cells, and CCK-BR, mostly in the stomach and nervous system tissues, have been identified as the endogenous receptors of CCK. Both have high affinity for the sulfated CCK octapeptide (CCK-8), whereas only the CCK-BR has high affinity for gastrin.
CCK is a peptide hormone discovered in the small intestine. Together with secretin and gastrin, CCK constitutes the classical gut hormone triad. In addition to gallbladder contraction, CCK also regulates pancreatic enzyme secretion and growth, intestinal motility, satiety signalling and the inhibition of gastric acid secretion. CCK is also a transmitter in central and intestinal neurons.