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Role of Alpha‐Adrenergic Vasoconstriction in Regulating Skeletal Muscle Blood Flow during Single Leg Knee Extension Exercise with Advancing Age
Author(s) -
Ratchford Stephen M,
Clifton Heather L,
BarretO'Keefe Zachary M,
Broxterman Ryan M,
Gifford Jayson R,
Hydren Jay R,
Rossman Matthew J,
Ives Stephen J,
Trinity Joel D,
Witman Melissa AH,
Garten Ryan S,
Morgan David E,
Nelson Ashley D,
Richardson Russell S,
Wray David Walter
Publication year - 2017
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.31.1_supplement.712.5
Subject(s) - medicine , phentolamine , vasoconstriction , vasodilation , blood flow , blockade , hemodynamics , skeletal muscle , heart rate , blood pressure , adrenergic , sympathetic nervous system , adrenergic antagonist , cardiology , propranolol , anesthesia , receptor
Background Aging is associated with augmented sympathetic nervous system activity, which promotes vasoconstriction in the peripheral circulation through the alpha‐adrenergic pathway. However, whether this age‐related sympathoexcitation restrains exercising skeletal muscle blood flow and vascular conductance remains poorly understood. Methods In nine young (4F/5M, 25 ± 5 yr, 178 ± 8 cm, 73 ± 12 kg) and seven old (2F/5M, 63 ± 11 yr, 175 ± 9 cm, 78 ± 15 kg) healthy volunteers, we evaluated changes in leg blood flow (LBF, Doppler ultrasound), mean arterial pressure (MAP) and leg vascular conductance (LVC) before and after femoral intra‐arterial infusion of phentolamine (a nonselective alpha‐adrenergic antagonist) at rest and during knee‐extensor exercise (0, 5, and 10W). Results are presented as the change from control to adrenergic blockade conditions. Results At rest, similar increases in LBF (269 ± 45 vs. 250 ± 60 ml/min, young vs. older) and LVC (3.4 ± 0.6 vs. 2.9 ± 0.6 ml/min/mmHg, young vs. old) were observed between groups following the adrenergic blockade. During exercise, the adrenergic blockade increased LBF to a similar degree in both young (0W: 330 ± 116, 5W: 178 ± 130, and 10W: 239 ± 127ml/min) and old (0W: 209 ± 57, 5W: 251 ± 22, and 10W: 165 ± 75 ml/min), with no difference between work rates in either group. Similarly, LVC increased as a consequence of the adrenergic blockade in both young (0W: 4.6 ± 1.2, 5W: 3.0 ± 1.2, and 10W: 3.1 ± 1.2 ml/min/mmHg) and old (0W: 3.6 ± 1.1, 5W: 4.2 ± 0.9, and 10W: 3.8 ± 0.9 ml/min/mmHg), with no difference between work rates. Both at rest and during exercise, MAP did not differ between groups or as a consequence of drug administration. Conclusions Using a pharmacologic approach to locally block alpha adrenergic vasoconstriction, we observed a similar drug‐induced change in leg hemodynamics in both the young and old groups. These data suggest that sympathetic restraint of limb blood flow persists during small muscle mass exercise, and that this adrenergic response is not impacted by advancing age. Support or Funding Information Funded in part by the National Institutes of Health (HL118313) and the U.S. Department of Veterans Affairs (RX001697, RX001418, E6910R).