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Is Sympathetic Restraint of Skeletal Muscle Blood Flow Present During Exercise?
Author(s) -
BarrettO'Keefe Zachary,
Ives Stephen J.,
Trinity Joel D.,
Witman Melissa A.H.,
Rossman Matthew J.,
Groot H. Jonathan,
Morgan David E.,
Gmelch Benjamin,
Richardson Russell S.,
Wray David Walter
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1136.2
Subject(s) - medicine , blood flow , vasoconstriction , blood pressure , skeletal muscle , vasodilation , phentolamine , phenylephrine , endocrinology , hemodynamics , anesthesia , cardiology , receptor
To better define the role of sympathetic vasoconstriction in the regulation of exercising skeletal muscle blood flow, five healthy men (24 ± 1 yrs) performed knee‐extensor exercise at 0, 5, 10, and 15 watts during intra‐arterial infusion of phenylephrine (PE, alpha‐1 agonist), phentolamine (PHEN, non‐selective alpha adrenergic antagonist), and saline. Arterial blood pressure, leg blood flow (Doppler ultrasound), and leg vascular conductance were determined continuously. During exercise, PE‐mediated reductions in leg blood flow (−27 ± 11, −22 ± 9, −8 ± 8, −13 ± 9% at 0, 5, 10, and 15W, respectively) and vascular conductance (−27 ± 11, −23 ± 9, −9 ± 8, −13 ± 9%) were blunted in an intensity‐dependent manner. In contrast, PHEN administration provoked a 30–40% increase in both leg blood flow (32 ± 8, 40 ± 12, 42 ± 12, 35 ± 9%) and leg vascular conductance (38 ± 10, 45 ± 14, 44 ± 12, 36 ± 9%) that persisted during all exercise intensities. Arterial blood pressure remained unchanged throughout all drug infusions. Together, these data support the concept of “functional sympatholysis” during exercise, but indicate a more prominent role for endogenous, alpha receptor‐mediated restraint of skeletal muscle blood flow than has been reported previously. Research support from NIH PO1 HL‐091830, VA RR&D E6910R, and AHA 0835209N.