Effect of a novel experience prior to training or testing on retention of an inhibitory avoidance response in mice: involvement of an opioid system.
These experiments examined the effects of a novel experience prior to training or retention testing on 24-h retention of an inhibitory avoidance response in mice. The experiments were based on previous evidence that novel training experiences release hypothalamic beta-endorphin. When given 1 h prior to training, the novel experience (clinging to the wire-mesh ceiling and exploring a small box) attenuated the memory-enhancing effects of post-training administration of naloxone as well as the enhancing effects of beta-endorphin administered prior to the retention test. The novel experience given prior to training did not block the enhancing effects of post-training administration of epinephrine. beta-Endorphin and the novel experience both enhanced retention performance when administered 1 h (as well as 3 but not 6 h) prior to the retention test. The enhancement found with both treatments was blocked by simultaneous administration of naloxone or by administration of propranolol a few minutes prior to the retention test. The findings of these experiments are consistent with the view that the effects of the novel experience are due to a release of endogenous beta-endorphin and provide additional evidence that the effects, on retention, of naloxone given post-training and beta-endorphin given prior to a retention test, are based on training-induced release of beta-endorphin.
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D004723:Endorphins / Q000378:metabolism / Q000494:pharmacology*; D004837:Epinephrine / Q000494:pharmacology; D005106:Exploratory Behavior / Q000502:physiology*; D008297:Male; D008568:Memory / Q000187:drug effects*; D051379:Mice; D008815:Mice, Inbred Strains; D009270:Naloxone / Q000494:pharmacology; D012153:Retention, Psychology / Q000187:drug effects*; D013997:Time Factors
D004723:Endorphins; D009270:Naloxone; D004837:Epinephrine