Abstract
We investigated the integration of sympathetic vasoconstriction and local vasodilation in the skeletal muscle and skin microvasculature of humans. In 39 healthy volunteers, we simultaneously measured the blood flow index in the flexor carpi radialis muscle using diffuse correlation spectroscopy and the skin using laser‐Doppler flowmetry. We examined the effects of acute sympathoexcitation induced by forehead cooling on relatively weak and robust vasodilatory responses during postocclusive reactive hyperemia (PORH) induced by 70‐sec and 10‐min arterial occlusion in the upper arm. To increase sympathetic tone during PORH, forehead cooling was begun 60 sec before the occlusion release and ended 60 sec after the release. In the 70‐sec occlusion trials, acute sympathoexcitation reduced the peak and duration of vasodilation in both skeletal muscle and skin. The inhibition of vasodilation by sympathoexcitation was blunted in both tissues by the robust vasodilatory stimulation produced by the 10‐min occlusion, and the degree of blunting was greater in skeletal muscle than in skin, especially the initial and peak responses. Sympathoexcitation reduced the peak vasodilation only in skin, while it accelerated the initial vasodilation only in skeletal muscle. However, the decline in vasodilation after the peak was significantly hastened in skeletal muscle, shortening the duration of the vasodilation. We conclude that, in humans, the integration of sympathetic vasoconstriction and local vasodilation has different effects in skeletal muscle and skin and is likely an important contributor to the selective control of perfusion in the microcirculations of different tissues.
Highlights
A rapid marked increase in limb blood flow is observed following ischemia caused by temporary arterial occlusion
The percentage changes in peak blood flow index (BFI) and muscle vascular conductance (MVC) elicited by forehead cooling were significantly larger in the 10-min than the 70-sec occlusion trials, whereas the percentage changes in peaks laser-Doppler flow (LDF) and Cutaneous vascular conductance (CVC) were similar in the two trials
To the best of our knowledge, this is the first study examining the effect of acute sympathoexcitation on local vasodilation in both the skeletal muscle and skin a 2019 The Authors
Summary
A rapid marked increase in limb blood flow is observed following ischemia caused by temporary arterial occlusion. The integrated effects of local vasodilation and sympathetic vasoconstriction in skeletal muscle and skin may be deeply involved in determining the distribution of blood flow to these tissues and in systemic arterial blood pressure regulation. We investigated the effects of increased sympathetic tone on vasodilatory responses within the forearm skeletal muscle and skin microvasculature during PORH. For this purpose, we used DCS and laser-Doppler flowmetry to simultaneously measure blood flow in the skeletal muscle and skin microcirculations.
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