Document Detail

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans.
MedLine Citation:
PMID:  23292718     Owner:  NLM     Status:  MEDLINE    
Previous studies in humans attempting to assess sympathetic vascular transduction have related large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) to associated changes in limb vascular resistance. However, such procedures do not provide insight into the ability of MSNA to dynamically control vascular tone on a beat-by-beat basis. Thus we examined the influence of spontaneous MSNA bursts on leg vascular conductance (LVC) and how variations in MSNA burst pattern (single vs. multiple bursts) and burst size may affect the magnitude of the LVC response. In 11 young men, arterial blood pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 min of supine rest. Signal averaging was used to characterize percent changes in LVC for 15 cardiac cycles following heartbeats associated with and without MSNA bursts. LVC significantly decreased following MSNA bursts, reaching a nadir during the 6th cardiac cycle (single bursts, -2.9 ± 1.1%; and multiple bursts, -11.0 ± 1.4%; both, P < 0.001). Individual MSNA burst amplitudes and the total amplitude of consecutive bursts were related to the magnitude of peak decreases in LVC. In contrast, cardiac cycles without MSNA bursts were associated with a significant increase in LVC (+3.1 ± 0.5%; P < 0.001). Total vascular conductance decreased in parallel with LVC also reaching a nadir around the peak rise in arterial blood pressure following an MSNA burst. Collectively, these data are the first to assess beat-by-beat sympathetic vascular transduction in resting humans, demonstrating robust and dynamic decreases in LVC following MSNA bursts, an effect that was absent for cardiac cycles without MSNA bursts.
Seth T Fairfax; Jaume Padilla; Lauro C Vianna; Michael J Davis; Paul J Fadel
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2013-01-04
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  304     ISSN:  1522-1539     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-03-04     Completed Date:  2013-04-18     Revised Date:  2014-03-07    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H759-66     Citation Subset:  IM    
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MeSH Terms
Blood Pressure / physiology
Femoral Artery / innervation*,  physiology*
Heart Rate / physiology
Muscle, Skeletal / blood supply*,  innervation
Pulsatile Flow / physiology
Regional Blood Flow / physiology
Rest / physiology*
Sympathetic Nervous System / physiology*
Vascular Resistance / physiology*
Young Adult
Grant Support

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