Abstract
Posttrial administration of 40 mg/kg and 100 mg/kg, but not of 1 mg/kg, of morphine hydrochloride facilitates learning of a one-trial passive avoidance task in drug-naive mice. The effect does not depend on the punishing properties of the morphine injection, since an injection of LiCl (a strong punisher) fails to enhance learning in a similar way. After the establishment of tolerance by several morphine administrations, the 100 mg/kg, but not the 40 mg/kg, dose level resulted in memory facilitation.
The data are discussed in connection with the hypothesis that morphine acts directly on reinforcement mechanisms by activating the opiate receptor.
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Mondadori, C., Waser, P.G. Facilitation of memory processing by posttrial morphine: Possible involvement of reinforcement mechanisms?. Psychopharmacology 63, 297–300 (1979). https://doi.org/10.1007/BF00433566
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DOI: https://doi.org/10.1007/BF00433566