Interference with visual memory in rats following infusion of the functional NMDA receptor antagonist, HA-966, into temporal regions

Results from lesion studies show that selective damage to the temporal cort ex or lateral entorhinal cortex impairs visual memory, whereas damage to th e hippocampal region does not affect retention of a visual discrimination t ask, Major input pathways of the above structures use glutamate as neurotra nsmitter. The glutamate NMDA receptor appears to play an important role for cognitive functions, The objective of the present study was to examine whe ther microinjections of the functional NMDA receptor antagonist, 3-amino-1- hydroxy-2-pyrrolidinone ((+)-HA-966), might result in effects mimicking tho se seen in lesion studies, The results show that infusion of HA-966 into th e temporal cortex or lateral entorhinal cortex 1.5-3 h after the learning c riterion had been obtained led to an impeded visual memory when tested 13 d ays later, whereas HA-966 infused into the hippocampal region did not affec t memory. A similar retention deficit with HA-966 infusions in the temporal cortex or lateral entorhinal cortex was seen when testing took place 23 da ys later, whereas a markedly weaker effect was observed when the retention period was reduced to 3 days. It is suggested that the hippocampal region i s a temporary storing site for nonspatial memory engrams, and later posttra ining memory consolidation involves the temporal and lateral entorhinal cor tices. Furthermore, the degree of the effect of HA-966 is related to the le ngth of the retention period. (C) 2001 Elsevier Science BN. All rights rese rved.