Dual action of post-training naloxone on memory.
Naloxone administered at a dose of 0.2 mg/kg post-training antagonizes the deleterious effect of post-training beta-endorphin administration and prevents the enhancing effect of pretest beta-endorphin administration, on retention of a step-down inhibitory avoidance task in rats. Given at a higher dose (0.4 mg/kg), naloxone caused, in addition to these effects, a pronounced retrograde facilitation which was additive with that caused by post-training ACTH or epinephrine administration. These findings show that post-training naloxone has two different effects or sets of effects, each with a different dose threshold: An interference with beta-endorphin induced state dependency and a true modulatory effect.
Izquierdo
I
I
Centro de Memoria, U.F.R.G.S., Porto Alegre, RS, Brazil.
Netto
C A
CA
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D008568:Memory / Q000187:drug effects*; D011939:Mental Recall / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects*; D001615:beta-Endorphin / Q000037:antagonists & inhibitors / Q000494:pharmacology
D011957:Receptors, Opioid; D009270:Naloxone; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D004837:Epinephrine