Abstract
Aging differentially affects receptor function. In the present electrophysiological study we compared neuronal responsiveness to locally applied dopamine D 1 and D 2 receptor agonist in the striatum of female Fischer 344 rats aged 3 and 26–27 months. In a subgroup of the old rats, the nigrostriatal dopamine bundle was destroyed unilaterally with 6-hydroxydopamine (6-OHDA) to assess receptor plasticity in response to denervation. Spontaneous firing rate of striatal neurons was higher in aged compared to young rats. Higher doses of the D 1 agonist SKF 38393 or the D 2 agonist quinpirole were required to elicit a 50% change in firing rate in aged compared to young rats. No difference with SKF 38393 or quinpirole was detected between 6-OHDA denervated and control (nonlesioned) striatum in aged rats. Supersensitivity to D 2 agonists has been reported following 6-OHDA lesions in young rats. These observations suggest that D 2 receptors in aged rat striatum might not be as plastic as in younger rats.
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