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Adrenergic control of vascular resistance varies in muscles composed of different fiber types: influence of the vascular endothelium

Adrenergic control of vascular resistance varies in muscles composed of different fiber types:... Abstract The influence of the sympathetic nervous system (SNS) upon vascular resistance is more profound in muscles comprised predominately of low-oxidative type IIB vs. high-oxidative type I fiber types. However, within muscles containing high-oxidative type IIA and IIX fibers, the role of the SNS on vasomotor tone is not well established. The purpose of this study was to examine the influence of sympathetic neural vasoconstrictor tone in muscles composed of different fiber types. In adult male rats, blood flow to the red and white portions of the gastrocnemius (Gast Red and Gast White , respectively) and the soleus muscle was measured pre- and postdenervation. Resistance arterioles from these muscles were removed, and dose responses to α 1 -phenylephrine or α 2 -clonidine adrenoreceptor agonists were determined with and without the vascular endothelium. Denervation resulted in a 2.7-fold increase in blood flow to the soleus and Gast Red and an 8.7-fold increase in flow to the Gast White . In isolated arterioles, α 2 -mediated vasoconstriction was greatest in Gast White (∼50%) and less in Gast Red (∼31%) and soleus (∼17%); differences among arterioles were abolished with the removal of the endothelium. There was greater sensitivity to α 1 -mediated vasoconstriction in the Gast White and Gast Red vs. the soleus, which was independent of whether the endothelium was present. These data indicate that 1 ) control of vascular resistance by the SNS in high-oxidative, fast-twitch muscle is intermediate to that of low-oxidative, fast-twitch and high-oxidative, slow-twitch muscles; and 2 ) the ability of the SNS to control blood flow to low-oxidative type IIB muscle appears to be mediated through postsynaptic α 1 - and α 2 -adrenoreceptors on the vascular smooth muscle. adrenergic receptors clonidine phenylephrine blood flow Copyright © 2011 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Regulatory, Integrative and Comparative Physiology The American Physiological Society

Adrenergic control of vascular resistance varies in muscles composed of different fiber types: influence of the vascular endothelium

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References (44)

Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0363-6119
eISSN
1522-1490
DOI
10.1152/ajpregu.00205.2011
pmid
21677269
Publisher site
See Article on Publisher Site

Abstract

Abstract The influence of the sympathetic nervous system (SNS) upon vascular resistance is more profound in muscles comprised predominately of low-oxidative type IIB vs. high-oxidative type I fiber types. However, within muscles containing high-oxidative type IIA and IIX fibers, the role of the SNS on vasomotor tone is not well established. The purpose of this study was to examine the influence of sympathetic neural vasoconstrictor tone in muscles composed of different fiber types. In adult male rats, blood flow to the red and white portions of the gastrocnemius (Gast Red and Gast White , respectively) and the soleus muscle was measured pre- and postdenervation. Resistance arterioles from these muscles were removed, and dose responses to α 1 -phenylephrine or α 2 -clonidine adrenoreceptor agonists were determined with and without the vascular endothelium. Denervation resulted in a 2.7-fold increase in blood flow to the soleus and Gast Red and an 8.7-fold increase in flow to the Gast White . In isolated arterioles, α 2 -mediated vasoconstriction was greatest in Gast White (∼50%) and less in Gast Red (∼31%) and soleus (∼17%); differences among arterioles were abolished with the removal of the endothelium. There was greater sensitivity to α 1 -mediated vasoconstriction in the Gast White and Gast Red vs. the soleus, which was independent of whether the endothelium was present. These data indicate that 1 ) control of vascular resistance by the SNS in high-oxidative, fast-twitch muscle is intermediate to that of low-oxidative, fast-twitch and high-oxidative, slow-twitch muscles; and 2 ) the ability of the SNS to control blood flow to low-oxidative type IIB muscle appears to be mediated through postsynaptic α 1 - and α 2 -adrenoreceptors on the vascular smooth muscle. adrenergic receptors clonidine phenylephrine blood flow Copyright © 2011 the American Physiological Society

Journal

AJP - Regulatory, Integrative and Comparative PhysiologyThe American Physiological Society

Published: Sep 1, 2011

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