Morphine and memory in DBA/2 mice: effects of stress and of prior experience.
In a first set of experiments, immediately post-training morphine (1.0 or 2.5 but not 0.5 mg/kg) treatment, or immobilization stress (30 or 60 but not 15 min) impaired memory processes of non-pretrained DBA/2 mice tested in a passive avoidance box. The effects were naloxone-reversible and time-dependent (they were absent in mice injected with morphine, or immobilized, starting 120 min after training). No effect was evident in no-footshock groups injected with morphine (2.5 mg/kg) or immobilized (60 min), thus showing lack of proactive influence of the treatments on performance. In a second set of experiments, in which pretrained animals were used, both morphine and immobilization stress were less effective in disrupting memory processes of mice. In both sets of experiments a per se ineffective stress enhanced the effects of morphine. A number of possible hypotheses concerning the results obtained are examined. In particular the possible role of emotional factors in the effects of morphine on memory is discussed.
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced / Q000209:etiology*; D051379:Mice; D008811:Mice, Inbred DBA; D009020:Morphine / Q000037:antagonists & inhibitors / Q000633:toxicity*; D009270:Naloxone / Q000008:administration & dosage; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000150:complications* / Q000503:physiopathology
D009270:Naloxone; D009020:Morphine