ENHANCEMENT OF INHIBITORY AVOIDANCE RETENTION IN A 3-SESSION PARADIGMIS AFFECTED NEITHER BY NMDA RECEPTOR ANTAGONISM NOR BY GABA(A) RECEPTOR ACTIVATION IN THE HIPPOCAMPUS

We evaluated the effects of NMDA receptor blockade and GABA(A) recepto r activation in the hippocampus on the enhancement of retention on a s tep-down inhibitory avoidance task. Adult male Wistar rats were submit ted to two training sessions followed by a test session in a step-down inhibitory avoidance task (0.2 mA footshock, 34 h interval between se ssions). Immediately after the second session, animals received a bila teral intrahippocampal 0.5 mu L microinjection of vehicle, AP5 (5.0 mu g), or muscimol (0.03 mu g) Retention test performance improved in al l three experimental groups. There were no significant differences bet ween groups in any of the sessions: The results suggest that the enhan cement of inhibitory avoidance retention induced by additional trainin g does not depend on NMDA receptors and is not sensitive to GABA(A) re ceptor activation in the hippocampus.