Effect of beta-funaltrexamine on retention of passive-avoidance conditioning

Rats received administration of an opiate antagonist immediately following single-trial passive-avoidance training. Retention of passive-avoidance conditioning was assessed 1 week after training. Compared to noninjected and vehicle-injected control groups, post-training naloxone (2.0 mg/kg) administration significantly increased retention. A comparable facilitation of retention was also observed when animals received post-training administration of beta-funaltrexamine (40 mg/kg). These data provide additional support for mu opiate receptor activity in the regulation of memory processes.