10 - Cholecystokinin Receptors: Radioligand Binding and Affinity Labeling

Abstract

Publisher Summary Cholecystokinin (CCK) is a linear polypeptide hormone of neural and gastrointestinal origin. Receptors for cholecystokinin have been reported in various regions of the brain and spinal cord as well as in numerous locations along the gastrointestinal tract, including pancreatic acinar cells and islets, gallbladder smooth muscle, sphincter of Oddi, and smooth muscle and intrinsic nerves at the levels of the esophagus, stomach, small intestine, and colon. The classic physiological responses to cholecystokinin have been studied in the contraction of gallbladder smooth muscle and the secretion of zymogens by the exocrine pancreas, as well as in ileal strip contraction. There are two major types of CCK/gastrin receptors, which are classified as the “A” or “alimentary”-type receptor and the “B” or predominant “brain”-type receptor. The type A receptor is present on the pancreatic acinar cell and gallbladder smooth muscle as well as on pyloric smooth muscle, some peripheral neurons, and a few select brain nuclei. The type B receptor is widely distributed throughout the brain and represents the predominant CCK-binding receptor there.