Alpha- and beta-adrenergic receptors of the rat cerebral cortex and cerebral microvessels in aging, and their response to denervation.

We studied the effects of aging and norepinephrine depletion 2 weeks after unilateral locus ceruleus lesion on alpha 1-, alpha 2- and beta-adrenergic receptors by ligand binding methods in the ipsilateral and contralateral cerebral cortex of Fischer-344 rats. We also studied the effects of aging and noradrenergic denervation on beta-adrenergic receptors in isolated cerebral microvessels. We found that specific [125I]HEAT binding to alpha 1-adrenergic receptors was not affected by aging or by norepinephrine depletion. Although aging also had no effect on the density or affinity of [3H]UK-14,304 and [125I]pindolol binding to alpha 2- and beta-adrenergic receptors, the density of receptors increased significantly in all age groups after noradrenergic denervation. beta-Adrenergic receptors of cerebral microvessels also were unaffected by aging, but increased their density after noradrenergic denervation at all ages. In all instances, there were no significant effects on the affinity of ligand binding. We conclude that aging does not affect the density or the affinity of adrenergic receptors in the cerebral cortex of Fischer-344 rats, nor does it affect the response of these receptors to norepinephrine depletion.