CCKAR (cholecystokinin A receptor) is a G protein-coupled receptor located on chromosome 4 that mediates the physiological actions of cholecystokinin (CCK) in both peripheral and central nervous systems 1. In the gastrointestinal tract, CCKAR is predominantly expressed in the gallbladder and small intestine, where it regulates gallbladder contraction and emptying, pancreatic enzyme secretion, and intestinal motility through phosphatidylinositol-calcium second messenger signaling 2. CCKAR exhibits approximately 1000-fold higher affinity for CCK than gastrin, distinguishing it from the CCK-B receptor 1. In the central nervous system, CCKAR contributes to regulation of satiety, anxiety, analgesia, and dopamine-mediated behaviors, with some evidence suggesting involvement in cognitive processes 1, 3. At the cellular level, CCKAR mediates sex hormone-responsive regulation of social behaviors in specific neuronal populations, including ventromedial hypothalamus neurons expressing estrogen receptor 1 that are essential for mating behavior in females 4. Clinically, CCKAR dysfunction is highly relevant to cholesterol gallstone disease; genetic variants in CCKAR are associated with increased gallstone susceptibility, and the gene has been identified as Lith13, a major gallstone susceptibility locus 2. CCKAR polymorphisms have also been investigated in relation to alcohol withdrawal-associated hallucinations 5. Naturally occurring CCKAR gene disruption in OLETF rats results in hyperglycemia, hyperinsulinemia, and obesity phenotypes resembling non-insulin-dependent diabetes mellitus 6.