Blunted Sympathetic Vasoconstriction in Contracting Skeletal Muscle of Healthy Humans: is Nitric Oxide Obligatory?
Open Access
- 1 November 2003
- journal article
- clinical trial
- Published by Wiley in The Journal of Physiology
- Vol. 553 (1), 281-292
- https://doi.org/10.1113/jphysiol.2003.049940
Abstract
We tested the hypothesis that nitric oxide (NO) is responsible for blunting sympathetic α-adrenergic vasoconstriction in the active muscles of humans (functional sympatholysis). We measured forearm blood flow (Doppler ultrasound) and calculated the reductions in forearm vascular conductance (FVC) in response to α-adrenergic receptor stimulation during rhythmic handgrip exercise and during a control non-exercise vasodilator condition (intra-arterial adenosine), before and after local NO synthase (NOS) inhibition in healthy men. The forearm vasoconstrictor responses to endogenous noradrenaline release (intra-arterial tyramine) were significantly blunted during moderate exercise compared with adenosine, and these vasoconstrictor responses were not restored by NOS inhibition with NG-monomethyl-l-arginine (l-NMMA; n = 6) or NG-nitro-l-arginine methyl ester (l-NAME; n = 8). Similarly, l-NAME did not restore the vasoconstrictor responses to tyramine in contracting muscle during heavy rhythmic handgrip exercise (n = 4). In four additional subjects, we also found that the vasoconstrictor responses evoked by tyramine during exercise or adenosine were repeatable in the absence of NOS inhibition (i.e. time control). Finally, in five subjects the forearm vasoconstrictor responses to direct α1-adrenergic (phenylephrine) and α2-adrenergic (clonidine) receptor stimulation were blunted during moderate exercise compared with adenosine; these responses were also unaffected by l-NAME. Taken together, our results demonstrate that NO is not obligatory for functional sympatholysis in contracting skeletal muscles of healthy men.Keywords
This publication has 49 references indexed in Scilit:
- Interaction between sympathetic nerve activation and muscle fibre contraction in resistance vessels of hamster retractor muscleThe Journal of Physiology, 2003
- Rapid ReportThe Journal of Physiology, 2003
- α1- and α2-adrenergic vasoconstriction is blunted in contracting human muscleThe Journal of Physiology, 2003
- Skeletal muscle blood flow in humans and its regulation during exerciseActa Physiologica Scandinavica, 1998
- Nitric oxide mediates contraction‐induced attenuation of sympathetic vasoconstriction in rat skeletal muscleThe Journal of Physiology, 1998
- ATP-sensitive potassium channels mediate contraction-induced attenuation of sympathetic vasoconstriction in rat skeletal muscle.JCI Insight, 1997
- NEURAL CONTROL OF MUSCLE BLOOD FLOW: IMPORTANCE DURING DYNAMIC EXERCISEClinical and Experimental Pharmacology and Physiology, 1997
- Influence of prostaglandins on vasoconstrictor responses in the hindquarters vascular bed of the catProstaglandins and Medicine, 1981
- The Effect in Humans of Increased Sympathetic Activity on the Blood Flow to Active MusclesActa Medica Scandinavica, 1967
- Blood Pressure during Supine Exercise in Idiopathic Orthostatic HypotensionCirculation, 1961