State Dependent Learning and Morphine Tolerance

On the basis of a Pavlovian conditioning analysis of morphine tolerance, cues signaling the systemic effects of morphine come to elicit conditional pharmacological responses that attenuate the effect of the drug. Experiments were conducted to evaluate the relevance of this analysis to recent reports that morphine-experienced rats, anesthetized with pentobarbital prior to a final test injection of morphine, do not display the analgesic tolerance …