title: Unusual dose-related effect of an endorphin analog in a complex maze.
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000008:administration & dosage / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D007858:Learning / Q000187:drug effects*; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D001615:beta-Endorphin / Q000031:analogs & derivatives*
chemical_list: D004723:Endorphins; D009270:Naloxone; D001615:beta-Endorphin; C029416:endorphin, Ala-2-