Memory reactivation in rats treated with the 5-HT1A agonist 8-OH-DPAT: a case of gone, but not forgotten.

The effect of various doses of the serotonin-1A agonist 8-OH-DPAT at training on 72-hr retention of passive avoidance was investigated in rats. Results indicated impaired retention, as measured by latency to avoid shock. However, when total time spent in the nonshock compartment at test was assessed, the performance of drug-treated subjects was not significantly different than that of control animals. It is suggested that although drug treatment produced initial retention impairment, the memory trace for the aversive event was reactivated (i.e., "reminder effect") when subjects entered the shock compartment at test. These data imply that pharmacological treatments, especially those that modulate serotonergic neurotransmission, that appear to disrupt learning per se may interrupt neural circuits involved in retrieval processes.