The physiologic actions of the cholecystokinin (CCK) family of peptide hormones are mediated through two classes of G protein-coupled receptors GPCR), CCK-A R and CCK-B R. CCK-A R is a 428 amino acid protein with 7 putative transmembrane domains. This GPCR is involved in gall bladder contraction, insulin secretion, and has also been described in specific regions of the central nervous system. CCK-A R has been implicated in pancreatic tumorigenesis as well as the pathogenesis of eating disorders and drug addiction.