The effects of post-training naloxone administration upon shuttle avoidance performance in the rat.

Abstract

Endogenous opioid sUbstances have been demonstrated to have a profound affect on memory and learning alike. In the present study, naloxone hydrochloride was administered to rats intraperitoneally in one of two doses. The sUbjects received post-training doses of either 2.5 mg/kg or 10.0 mg/kg of naloxone and were tested for avoidance response retention in a shuttle paradigm. All animals receiving naloxone were compared to saline controls. The animals were tested for retention 24 hours following training as well as at one week and two weeks respectively. Results indicated that all animals remembered at the 24 hour retention trial. The groups did however differ from each other at one week post-training. Only the low dosage naloxone (2.5 mg/kg) group differed significantly from the other two groups. The low dosage naloxone group had significantly faster approach latencies than either the high dosage naloxone group or the saline group. The results are discussed in terms of behavioral evidence supporting the theory of multiple opiate receptors and in terms of long-term memory consolidation processes.