CHOLECYSTOKININ RECEPTOR-BINDING IN MORPHINE ANALGESIA - TOLERANCE, WITHDRAWAL AND ABSTINENCE

The effect of morphine treatment on cholecystokinin (CCK) receptor bin ding in rat cerebral cortex was investigated. Subcutaneous implantatio n and removal of Alzet miniosmotic pumps, releasing morphine, permitte d us to establish the phases of initial analgesia, tolerance to the an algesic action of morphine, morphine withdrawal and abstinence. CCK re ceptor binding in rat cerebral cortex never differed from the values o btained from animals implanted with saline-releasing minipumps. The re sults of the present study suggest that the putative changes in the in teraction between opioidergic and CCKergic neurotransmission at differ ent stages of morphine treatment and withdrawal are not caused by chan ges of CCK receptor binding properties.