CHRONIC INFUSIONS OF GABA INTO THE MEDIAL PREFRONTAL CORTEX INDUCE SPATIAL ALTERNATION DEFICITS IN AGED RATS

It has been proposed that functions associated with the prefrontal cor tex could change as a consequence of aging. Previous experiments in yo ung rats have demonstrated that anatomical lesions or chronic GABA inf usions into this area produce deficits in spatial delayed alternation tasks. The present study examines the effect of chronic (7 days) GABA or saline infusion into the prefrontal cortex on the performance of de layed alternation task in old rats (24 months). The results suggested that aged rats needed more sessions to acquire the delayed alternation task. GABA infusions into the prefrontal cortex produced deficits in spatial alternation tasks similar to those previously observed in youn g rats. Performance rapidly recovered after the infusion period. Histo logical analysis showed similar lesion size in both groups. The result s suggest that aged prefrontal cortex and/or related areas participati ng in the acquisition of the delayed alternation task are more sensiti ve to aging processes. Furthermore, the prefrontal cortex is important for the retention of a previously learned spatial delayed alternation task. The structures involved in functional recovery from these defic its appear to be fully functional in aged rats.