?-Adrenergic receptor activity of cerebral microvessels is reduced in aged rats

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Abstract
The effect of age on beta-(β) adrenergic receptor number (Bmax) and adenylate cyclase (AC) activity was determined in microvessels isolated from male F-344 rats at 3, 18, and 24 months of age. Scatchard analysis of [125I]iodocyanopindolol (ICYP) binding indicated reduced Bmax (fmol/mg) of microvessels isolated from 24 month old rats (27.2±4.9) compared with 3 month old (50.4±5.2) and 18 month old rats (p<0.01) (61.4±7.6). The basal AC activity (pmol cAMP/mg) in 24 month old rats (32.0 ±6.7) and in 18 month old rats (30.4±2.1) were significantly reduced compared to the basal activity in the young (50.1±4.2). The net isoproterenol or NaF stimulated AC activity in 24 month old rats (zero and 15.6±8.5 respectively) was also reduced compared to young rats (10.1±3.9 and 166.0±21.2 respectively). It is concluded that aging is associated with reduced isoproterenol stimulated AC activity of cerebral microvessels. This reduction is the product of reduced β-adrenergic receptor number and reduced activity of AC in aged rat cerebral microvessels.