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Influence of α-adrenergic vasoconstriction on the blunted skeletal muscle contraction-induced rapid vasodilation with aging
Journal article   Open access   Peer reviewed

Influence of α-adrenergic vasoconstriction on the blunted skeletal muscle contraction-induced rapid vasodilation with aging

Darren P Casey and Michael J Joyner
Journal of applied physiology (1985), Vol.113(8), pp.1201-1212
10/15/2012
DOI: 10.1152/japplphysiol.00734.2012
PMCID: PMC3472494
PMID: 22961267
url
https://doi.org/10.1152/japplphysiol.00734.2012View
Published (Version of record) Open Access

Abstract

We tested the hypothesis that elevated sympathetic tone is responsible for lower peak vasodilation after single muscle contractions in older adults. Young (n = 13, 7 men and 6 women, age: 27 ± 1 yr) and older (n = 13, 7 men and 6 women, age: 69 ± 2 yr) adults performed single forearm contractions at 10%, 20%, and 40% of maximum during 1) control, 2) sympathetic activation via lower body negative pressure (LBNP; -20 mmHg), and 3) intra-arterial infusion of phentolamine (α-adrenergic antagonist). Brachial artery diameter and velocities were measured via Doppler ultrasound, and forearm vascular conductance (FVC; in ml·min(-1)·100 mmHg(-1)) was calculated from blood flow (in ml/min) and blood pressure (in mmHg). Peak vasodilator responses [change in (Δ) FVC from baseline] were attenuated in older adults at 20% and 40% of maximum (P < 0.05). LBNP reduced peak ΔFVC at 10% (98 ± 17 vs. 70 ± 12 ml·min(-1)·100 mmHg(-1)), 20% (144 ± 12 vs. 98 ± 3 ml·min(-1)·100 mmHg(-1)), and 40% (209 ± 20 vs. 161 ± 21 ml·min(-1)·100 mmHg(-1), P < 0.01 vs. control) in younger adults but not in older adults (71 ± 11 vs. 68 ± 11, 107 ± 13 vs. 106 ± 16, and 161 ± 22 vs. 144 ± 22 ml·min(-1)·100 mmHg(-1), respectively, P = 0.22-0.99). With phentolamine, peak ΔFVC was enhanced in older adults at each contraction intensity (100 ± 14, 147 ± 22, and 200 ± 26 ml·min(-1)·100 mmHg(-1), respectively, P < 0.01 vs. control) but not in younger adults (94 ± 13, 153 ± 13, and 224 ± 27 ml·min(-1)·100 mmHg(-1), respectively, P = 0.30-0.81 vs. control). Our data indicate that α-adrenergic vasoconstriction and/or blunted functional sympatholysis might contribute to the age-related decreases in skeletal muscle contraction-induced rapid vasodilation in humans.
 Sympathetic Nervous System - drug effects Humans Lower Body Negative Pressure - methods Male Adrenergic alpha-Antagonists - pharmacology Hemodynamics - physiology Heart Rate - drug effects Vasoconstriction - physiology Regional Blood Flow - drug effects Sympathetic Nervous System - physiology Muscle, Skeletal - drug effects Forearm - blood supply Heart Rate - physiology Adult Female Blood Pressure - drug effects Blood Pressure - physiology Brachial Artery - drug effects Forearm - physiology Vasodilation - physiology Muscle, Skeletal - blood supply Infusions, Intra-Arterial - methods Phentolamine - pharmacology Muscle, Skeletal - physiology Vasoconstriction - drug effects Aging - physiology Muscle Contraction - drug effects Muscle Contraction - physiology Aged Hemodynamics - drug effects Vasodilation - drug effects Regional Blood Flow - physiology Blood Flow Velocity - physiology Blood Flow Velocity - drug effects Brachial Artery - physiology

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