Age-related changes in striatal function of freely-moving F344 rats

Multi-wire electrode arrays were used to record extracellular electrophysio logical activity in striatal medium spiny-like neurons of freely-moving you ng (6-13 months) and aged (24-26 months) Fischer 344 rats. While overall ba sal firing rates did not differ between the two groups, d-amphetamine (5.0 mg/kg) increased firing rates more in the young rats. D-Amphetamine had het erogeneous effects on firing rates, however, exciting 63% of the neurons wh ile inhibiting 37%. Neurons were classified according to their response to d-amphetamine (excited vs. inhibited) to examine age-related differences in firing rates and bursting activity. In the d-amphetamine-excited neurons, pre-drug intraburst firing rates were higher in the old rats. This effect w as reversed by d-amphetamine. D-Amphetamine increased the percentage of spi kes within bursts to a greater extent in the aged animals and decreased bur st durations greater in the young group. In d-amphetamine-inhibited neurons , firing rates were diminished in the old rats more than they were in the y oung rats. These results demonstrate age-related alterations in striatal el ectrophysiological activity that may help explain motor deficits seen in se nescence. (C) 2001 Elsevier Science Inc. All rights reserved.