Cholecystokinin (CCK, previously called pancreozymin) (Takahashi Y et al,1985) is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. CCK is synthesized by I-cells in the small intestine and secreted in the duodenum, causing the release of digestive enzymes and bile from the pancreas and gall-bladder respectively. It also acts as a hunger suppressant. CCK receptors bind CCK. In humans, there are two receptor types, A (Ulrich CD et al, 1993) and B (Pisegna JR et al, 1992). The A type are primarily distributed in the GI tract whereas the B type are primarily in the CNS. In the CNS, type B receptors modulate anxiety, analgesia, arousal, and neuroleptic activity.These receptors mediates the action of CCK by association with G proteins that activate a phosphatidylinositol-calcium second messenger system.