Document Detail

alpha-adrenergic vasoconstriction in active skeletal muscles during dynamic exercise.
MedLine Citation:
PMID:  10409179     Owner:  NLM     Status:  MEDLINE    
Sympathetic vasoconstriction in working muscles during dynamic exercise has been demonstrated by intra-arterial administration of alpha(1)-adrenergic antagonists. The purpose of this study was to examine the existence of alpha(1)- and alpha(2)-adrenergic receptor-mediated vasoconstriction in active skeletal muscles during exercise. Six mongrel dogs were instrumented chronically with flow probes on the external iliac arteries of both hindlimbs, and a catheter was inserted in one femoral artery. All dogs ran on a motorized treadmill at three exercise intensities (3 miles/h, 6 miles/h, and 6 miles/h at 10% grade) on separate days. After 5 min of exercise, a selective alpha(1)- (prazosin) or a selective alpha(2)-adrenergic antagonist (rauwolscine) was infused as a bolus into the femoral arterial catheter (only one drug per day). The doses of the antagonists were adjusted to maintain the same effective concentration at each exercise intensity. At the mild, moderate, and heavy workloads prazosin infusion produced immediate increases in iliac conductance of 65 +/- 9, 35 +/- 6, and 18 +/- 4% (means +/- SE), respectively, and increases in blood flow of 290 +/- 24, 216 +/- 23, and 172 +/- 18 ml/min, respectively. Rauwolscine infusion produced increases in conductance of 52 +/- 5%, 36 +/- 5%, and 26 +/- 3%, respectively, and blood flow increases of 250 +/- 34, 244 +/- 39, and 259 +/- 35 ml/min at the three workloads. Systemic blood pressure and blood flow in the contralateral iliac artery were unaffected by any of the antagonist infusions. These results demonstrate that there is ongoing alpha(1)- and alpha(2)-adrenergic receptor-mediated vasoconstriction in exercising skeletal muscles even at heavy workloads and that the magnitude of vasoconstriction decreases as exercise intensity increases.
J B Buckwalter; P S Clifford
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  277     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1999 Jul 
Date Detail:
Created Date:  1999-08-30     Completed Date:  1999-08-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H33-9     Citation Subset:  IM; S    
Departments of Anesthesiology and Physiology, Medical College of Wisconsin and Veterans Affairs Medical Center, Milwaukee, Wisconsin 53295, USA.
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MeSH Terms
Adrenergic alpha-Antagonists / pharmacology
Muscle, Skeletal / drug effects,  physiology*
Physical Conditioning, Animal / physiology*
Prazosin / pharmacology
Receptors, Adrenergic, alpha / drug effects,  physiology*
Vasoconstriction / drug effects,  physiology*
Yohimbine / pharmacology
Reg. No./Substance:
0/Adrenergic alpha-Antagonists; 0/Receptors, Adrenergic, alpha; 146-48-5/Yohimbine; 19216-56-9/Prazosin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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