Cholecystokinin (CCK) is a neuropeptide which is widely distributed in the mammalian central nervous system. Two CCK receptors have been identified to mediate the effects of CCK/gastrin family: CCKA (or CCK-1) receptor and CCKB (or CCK-2 or gastrin receptor). The CCKB receptor is the predominant subtype in the CNS where it is widely distributed, however, it also occurs in abundance in the gastro-intestinal tract. CCKB receptors have been found to be most abundant in the cerebral cortex, cerebellum, basal ganglia, and amygdale. Animal and human studies using CCKB receptor antagonists have suggested that anxiety, panic attacks, analgesia, and satiety may be modulated through the CCKB receptor.