Retention of passive avoidance behavior in rats following α- and γ-endorphin administration: Effects of post-learning treatments

Abstract

Neuropeptides related to β-endorphin (β-LPH 61−91) profoundly affect avidance behavior. That γ- and α-endorphin (β-LPH 61–77 and β-LPH 61–76, respectively) influence memory processes, has been investigated on rats. Using a one-trial learning, step-through passive avoidance paradigm, it was found that γ-endorphin attenuates later retention of passive avoidance behavior when administered immediately or 3 h after learning; α-endorphin facilitates this response when given immediately after learning. Neither γ- nor α-endorphin influence retention when the treatment is postponed for 6 h after learning. These data are interpreted as suggesting an opposite effect of γ- and α-endorphin on consolidation processes.