Morphine-induced attenuation of morphine tolerance

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Science  26 Jun 1981:
Vol. 212, Issue 4502, pp. 1533-1534
DOI: 10.1126/science.7233244


Rats experienced both morphine and an environmental cue, but the cue always signaled a drug-free period. They were subsequently administered morphine in the presence of the cue, and the development of analgesic tolerance was assessed. The prior experience retarded such tolerance. The finding that a procedure of opiate administration can retard opiate tolerance suggests that an association between cues preceding the drug and the drug itself contributes to tolerance.