Retrograde amnesia caused by Met-, Leu- and des-Try-Met-enkephalin in the rat and its reversal by naloxone.
Immediate post-training i.p. injection of Met-enkephalin, Leu-enkephalin or des-Tyr-Met-enkephalin, caused retrograde amnesia for a shuttle avoidance task in rats. The effect was linearly related to the log of the dose between 0.32 and 2.0 microgram/kg, and the potency of the three compounds was similar (ED50 0.35-0.45 microgram/kg). Naloxone (0.2 mg/kg) antagonized the amnestic effect of the peptides. Since the log dose-response curves were displaced to the right in quasi-parallel fashion, and Lineweaver-Burk plots of the data showed an intersection very close to the origin of the horizontal axis, the antagonism between naloxone and the three peptides appears to be competitive.
D000647:Amnesia / Q000139:chemically induced*; D000648:Amnesia, Retrograde / Q000139:chemically induced*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D004336:Drug Antagonism; D004723:Endorphins / Q000494:pharmacology; D004743:Enkephalin, Leucine; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D006801:Humans; D007700:Kinetics; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C029668:enkephalin-Met, des-Tyr(1)-