Is sympathetic neural vasoconstriction blunted in the vascular bed of exercising human muscle?

Michael E. Tschakovsky, Kittiphong Sujirattanawimol, Stephen B. Ruble, Zoran Valic, Michael Joseph Joyner

Research output: Contribution to journalArticle

129 Citations (Scopus)

Abstract

Sympathetic vasoconstriction of muscle vascular beds is important in the regulation of systemic blood pressure. However, vasoconstriction during exercise can also compromise blood flow support of muscle metabolism. This study tested the hypothesis that local factors in exercising muscle blunt vessel responsiveness to sympathetic vasoconstriction. We performed selective infusions of three doses of tyramine into the brachial artery (n = 8) to evoke endogenous release of noradrenaline (norepinephrine) at rest and during moderate and heavy rhythmic handgrip exercise. In separate experiments, tyramine was administered during two doses of adenosine infusion (n = 7) and two doses of sodium nitroprusside (SNP) infusion (n = 8). Vasoconstrictor effectiveness across conditions was assessed as the percentage reduction in forearm vascular conductance (FVC), calculated from invasive blood pressure and non-invasive Doppler ultrasound blood flow measurements at the brachial artery. Tyramine evoked a similar dose-dependent vasoconstriction at rest in all three groups, with the highest dose resulting in a 42-46 % reduction in FVC. This vasoconstriction was blunted with increasing exercise intensity (e.g. tyramine high dose percentage reduction in FVC; rest -43.4 ± 3.7 %, moderate exercise -27.5 ± 2.3 %, heavy exercise -16.7 ± 3.6 %; P < 0.05). In contrast, tyramine infusion resulted in a greater percentage reduction in FVC during both doses of adenosine vs. rest (P < 0.05). Finally, percentage change in FVC was greater during low dose SNP infusion vs. rest (P < 0.05), but not different from rest at the high dose of SNP infusion (P = 0.507). A blunted percentage reduction in FVC during endogenous noradrenaline release in exercise but not vasodilator infusion indicates that sympathetic vasoconstriction is blunted in exercising muscle. This blunting appears to be exercise intensity-dependent.

Original languageEnglish (US)
Pages (from-to)623-635
Number of pages13
JournalJournal of Physiology
Volume541
Issue number2
DOIs
StatePublished - Jun 1 2002

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Vasoconstriction
Blood Vessels
Tyramine
Forearm
Muscles
Nitroprusside
Norepinephrine
Brachial Artery
Adenosine
Blood Pressure
Doppler Ultrasonography
Vasoconstrictor Agents
Vasodilator Agents

ASJC Scopus subject areas

  • Physiology

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Is sympathetic neural vasoconstriction blunted in the vascular bed of exercising human muscle? / Tschakovsky, Michael E.; Sujirattanawimol, Kittiphong; Ruble, Stephen B.; Valic, Zoran; Joyner, Michael Joseph.

In: Journal of Physiology, Vol. 541, No. 2, 01.06.2002, p. 623-635.

Research output: Contribution to journalArticle

Tschakovsky, Michael E. ; Sujirattanawimol, Kittiphong ; Ruble, Stephen B. ; Valic, Zoran ; Joyner, Michael Joseph. / Is sympathetic neural vasoconstriction blunted in the vascular bed of exercising human muscle?. In: Journal of Physiology. 2002 ; Vol. 541, No. 2. pp. 623-635.
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abstract = "Sympathetic vasoconstriction of muscle vascular beds is important in the regulation of systemic blood pressure. However, vasoconstriction during exercise can also compromise blood flow support of muscle metabolism. This study tested the hypothesis that local factors in exercising muscle blunt vessel responsiveness to sympathetic vasoconstriction. We performed selective infusions of three doses of tyramine into the brachial artery (n = 8) to evoke endogenous release of noradrenaline (norepinephrine) at rest and during moderate and heavy rhythmic handgrip exercise. In separate experiments, tyramine was administered during two doses of adenosine infusion (n = 7) and two doses of sodium nitroprusside (SNP) infusion (n = 8). Vasoconstrictor effectiveness across conditions was assessed as the percentage reduction in forearm vascular conductance (FVC), calculated from invasive blood pressure and non-invasive Doppler ultrasound blood flow measurements at the brachial artery. Tyramine evoked a similar dose-dependent vasoconstriction at rest in all three groups, with the highest dose resulting in a 42-46 {\%} reduction in FVC. This vasoconstriction was blunted with increasing exercise intensity (e.g. tyramine high dose percentage reduction in FVC; rest -43.4 ± 3.7 {\%}, moderate exercise -27.5 ± 2.3 {\%}, heavy exercise -16.7 ± 3.6 {\%}; P < 0.05). In contrast, tyramine infusion resulted in a greater percentage reduction in FVC during both doses of adenosine vs. rest (P < 0.05). Finally, percentage change in FVC was greater during low dose SNP infusion vs. rest (P < 0.05), but not different from rest at the high dose of SNP infusion (P = 0.507). A blunted percentage reduction in FVC during endogenous noradrenaline release in exercise but not vasodilator infusion indicates that sympathetic vasoconstriction is blunted in exercising muscle. This blunting appears to be exercise intensity-dependent.",
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