Document Detail

Sympathetic outflow to muscle in humans during short periods of microgravity produced by parabolic flight.
MedLine Citation:
PMID:  10444548     Owner:  NLM     Status:  MEDLINE    
We have investigated the changes in muscle sympathetic nerve activity (MSNA) from the tibial nerve during brief periods of microgravity (microG) for approximately 20 s produced by parabolic flight. MSNA was recorded microneurographically from 13 quietly seated human subjects with their knee joints extended in a jet aircraft simultaneously with the electrocardiogram, the blood pressure wave (measured with a Finapres), the respiration curve, and the thoracic fluid volume (measured by impedance plethysmography). During quiet and seated parabolic flight, MSNA was activated in hypergravity and was suppressed in microG phasically. At the entry to hypergravity at 2 G just before microG, the thoracic fluid volume was reduced by 3.2 +/- 3%, and the arterial blood pressure was lowered transiently and then gradually elevated from 89.5 +/- 1.7 to 100.2 +/- 1.7 mmHg, which caused the enhancement of MSNA by 91.4 +/- 14.2%. At the entry to microG, the thoracic fluid volume was increased by 3.4%, which lowered the mean blood pressure to 77.9 +/- 2.3 mmHg and suppressed the MSNA by 17.2%. However, this suppression lasted only approximately 10 s, followed by an enhancement of MSNA that continued for several seconds. We conclude that MSNA is suppressed and then enhanced during microG produced by parabolic flight. These changes in MSNA are in response not only to intrathoracic fluid volume changes but also to arterial blood pressure changes, both of which are caused by body fluid shifts induced by parabolic flight, and these changes are quite phasic and transient.
S Iwase; T Mano; J Cui; H Kitazawa; A Kamiya; S Miyazaki; Y Sugiyama; C Mukai; S Nagaoka
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  277     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1999 Aug 
Date Detail:
Created Date:  1999-09-23     Completed Date:  1999-09-23     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R419-26     Citation Subset:  IM; S    
Department of Autonomic Neuroscience, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan.
Space Flight Mission:
Flight Experiment; Parabolic Flight; manned; short duration
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MeSH Terms
Aerospace Medicine*
Blood Pressure / physiology
Blood Volume
Heart Rate / physiology
Muscle, Skeletal / innervation*
Sympathetic Nervous System / physiology*
Thorax / blood supply
Tibial Nerve / physiology
Time Factors

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

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