Aging, prefrontal cortex, and amino acid neurotransmitters: differential effects produced by electrical stimulation.

The purpose of the present study was to investigate the effects of electrical stimulation on the in vivo release of amino acid neurotransmitters in the prefrontal cortex of young (3-4 months) and aged (27-30 months) rats. In vivo push-pull perfusions were performed in the conscious animal. The levels of aspartate, glutamate, and glycine were analyzed by HPLC-fluorimetric detection. Electrical stimulation of the medial prefrontal cortex at the intensity of 0.3 mA produced a significant increase in the levels of aspartate, glutamate, and glycine in young but not aged rats. However, at the intensity of 0.6 mA, a significant delayed increase of these same amino acids was produced in the aged rats. These results support the existence of a differential effect of electrical stimulation on amino acid neurotransmitters in the prefrontal cortex of young and aged rats.