Effects of aging and exercise training on the dynamics of vasoconstriction in skeletal muscle resistance vessels

It is unknown whether aging or exercise training affect the dynamics of arteriolar vasoconstriction. Purpose We hypothesized that old age will slow, and exercise training will speed, the dynamics of skeletal muscle arteriolar vasoconstriction in resistance vessels of aged rats. Method Young (6 month old) and aged (24 month old) male Fischer-344 rats were assigned to sedentary (Sed: n = 6/age group) or exercise-trained (ET: n = 5 aged and 6 young; via treadmill running for 10–12 weeks) groups. After completion of training, arterioles from the red portion of the gastrocnemius muscle were removed, cannulated, and exposed to 10 −4 M norepinephrine (NE) or 20 mM caffeine. Changes in luminal diameter were recorded for analysis of constrictor dynamics. Result Old age blunted all kinetic parameters (i.e., time delay, time constant) resulting in vasoconstriction taking ~3 times as long to reach a steady state (SS) versus younger counterparts for NE (aged-sed: 15.6 ± 6.0 versus young-sed: 4.6 ± 0.5 s; P