alpha 1-Adrenergic-receptor responsiveness in skeletal muscle during dynamic exercise |
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Authors: | Buckwalter, John B. Mueller, Patrick J. Clifford, Philip S. |
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Abstract: | Attenuation of sympathetic vasoconstriction(sympatholysis) in working muscles during dynamic exercise iscontroversial. One potential mechanism is a reduction in1-adrenergic-receptorresponsiveness. The purpose of this study was to examine1-adrenergic-receptor-mediated vasoconstriction in resting and working skeletal muscles by using intra-arterial infusions of a selective agonist. Seven mongrel dogswere instrumented chronically with flow probes on the external iliacarteries of both hindlimbs and a catheter in one femoral artery. Aselective 1-adrenergic-receptoragonist (phenylephrine) was infused as a bolus into the femoral arterycatheter at rest and during exercise. All dogs ran on amotorized treadmill at two exercise intensities (3 and 6 miles/h).Intra-arterial infusions of the same effective concentration ofphenylephrine elicited reductions in vascular conductance of 76 ± 4, 76 ± 6, and 67 ± 5% (P > 0.05) at rest, 3 miles/h, and 6 miles/h, respectively. Systemic bloodpressure and blood flow in the contralateral iliac artery wereunaffected by phenylephrine. These results do not demonstrate anattenuation of vasoconstriction to a selective 1-agonist during exercise anddo not support the concept of sympatholysis. |
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