Failure of cholecystokinin to precipitate withdrawal in morphine-treated rats

In a test of the possible antagonistic interaction between cholecystokinin (CCK) and morphine, morphine-dependent rats were injected with one of three doses of CCK or with naloxone immediately following the consumption of a novel saccharin solution. Whereas opiate-dependent rats injected with the opiate antagonist naloxone acquired an aversion to the saccharin solution (and displayed a dramatic weight loss), CCK was without effect. These data were discussed in relation to the possible pharmacological antagonism between CCK and the opiates.