Lack of Transfer of Morphine Tolerance by Administration of Rat Cerebral Homogenates

Summary Transfer of tolerance to the analgesic effects of morphine to mice by injection of cerebral homogenates from morphine-tolerant rats was studied. After such pretreatment the mice were injected with a test dose of morphine and then tested for analgesia using the hot plate method. Neither the dose-response curve nor the mean increase in reaction time was significantly altered by pretreatment with the cerebral homogenate from morphine-tolerant rats. The possible reasons for the lack of confirmation of results obtained by other workers were discussed.