title: Facilitation of memory processing by posttrial morphine: possible involvement of reinforcement mechanisms?
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 in injection of LiCl (a strong punisher) fails to enhance learning in a similar way. After the establishment of tolerance by several morphone 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.
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D008094:Lithium / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects*; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D012054:Reinforcement, Psychology
chemical_list: D009020:Morphine; D008094:Lithium