Lack of interaction between cholecystokinin and opioid systems in the central control of breathing.

The present study investigates the interaction between CCK and opioid systems on the central control of breathing by analyzing the respiratory effects of CCK-8S (0.09 nmol) and met-enkephalin (0.7 and 1.4 mumol) applied to the ventral medullary surface of cats under the influence of the opiate antagonist naloxone and the CCK antagonist proglumide. Neither naloxone nor proglumide were able to modify the respiratory effects of CCK-8S and met-enkephalin, respectively. Therefore, the hypothesis that CCK and the opioid systems might operate as parallel and antagonic forces throughout the central nervous system, is no longer tenable.