Abstract
The sympathetic nervous system (SNS) has a profound ability to control blood flow and vascular resistance in skeletal muscle at rest and during exercise. The purpose of this study was to further elucidate the influence of the SNS on vasoconstrictor tone in muscles composed of different fiber types. Blood flow to the red (RGast) and white (WGast) portions of the gastrocnemius and the soleus muscles were measured pre‐ and post‐denervation, and dose‐response relations to alpha1 (phenylephrine) or alpha2 (clonidine) adrenoreceptor agonists were determined in isolated arterioles from these muscles. Denervation increased blood flow 8.7‐fold in the fast low‐oxidative muscle WGast while only eliciting an ∼2.7‐fold increase in the slow oxidative (soleus) and fast oxidative (RGast ) muscles. In arterioles, sensitivity to phenylephrine was greater in WGast and RGast versus the soleus muscle, whereas vasoconstriction to clonidine was greater in WGast (~50%) relative to that in RGast (~31%) and soleus (~17%). These data indicate 1) an intermediate control of vascular resistance by the SNS in fast oxidative muscle versus the other muscle types, and 2) the SNS influence on blood flow could fully account for the magnitude of the hyperemia observed during exercise in fast low‐oxidative muscle.
Published Version
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