INTRAHIPPOCAMPAL INFUSION OF THE NMDA RECEPTOR ANTAGONIST AP5 IMPAIRSRETENTION OF AN INHIBITORY AVOIDANCE TASK - PROTECTION FROM IMPAIRMENT BY PRETRAINING OR PREEXPOSURE TO THE TASK APPARATUS

The purpose of the present research was to further evaluate the role o f hippocampal N-methyl-D-aspartate (NMDA) receptors in inhibitory avoi dance task consolidation. Adult male Wistar rats were trained and test ed in a step-down inhibitory avoidance task (0.4 mA footshock, 24 h tr aining-test interval). Immediately after training, animals received a 0.5-mu l intrahippocampal infusion of the NMDA receptor antagonist ami nophosphonopentanoic acid (AP5) (5.0 mu g) or vehicle (phosphate buffe r in saline, pH 7.4). The infusion of AP5 impaired retention test perf ormance. Both pretraining with a low footshock intensity (0.2 mA) or p reexposure to the inhibitory avoidance box 24 h before training preven ted the amnestic effect of AP5. The results suggest that hippocampal N MDA receptors are critical for neither the enhancement of retention in duced by an additional training session nor the inhibitory avoidance r etention in animals that have previously learned about the task enviro nment by preexposure to the apparatus. (C) 1998 Academic Press.