Cholecystokinins (CCK) are derived from preprocholecystokinin. They are widely expressed in gastrointestinal tissues and in the CNS. There are two cholecystokinin receptors, referred to as A and B (CCKAR and CCKBR). CCKBR can be activated by the smaller CCK-4 (7, 8). In the CNS, CCKBR has been implicated in anxiety, depression, schizophrenia, depression, and opioid analgesia. In the stomach, CCK2 mediates gastrin-stimulated gastric acid secretion.