Cholecystokinin and pain: a review.

The recent discovery that cholecystokinin (CCK) is present in the nervous system has prompted studies that have nearly proven its neurotransmitter status. Pain modulation appears to be a major effect of CCK and proglumide, its antagonist. CCK's inhibitory effect and proglumide's potentiating effect on opiate analgesia may have clinical application; proglumide's inhibitory effect on opiate tolerance may help in management of chronic pain. More research is required before the CCK/opiate interaction can be exploited on a large scale to relieve pain.