Document Detail

Influence of age on the sympathetic neural adjustments to alterations in systemic oxygen levels in humans.
MedLine Citation:
PMID:  9277556     Owner:  NLM     Status:  MEDLINE    
We tested the hypothesis that aging influences the regulation of sympathetic nervous system activity (SNA) and arterial blood pressure during alterations in systemic O2 levels in humans. To accomplish this, we performed direct (intraneural) measurements of SNA to skeletal muscle (MSNA) in 10 young and 7 older healthy normotensive men during room air breathing (normoxic-control), moderate isocapnic hypoxemia [15 min of 10% fractional inspired O2 (FIO2)], and hyperoxemia (10 min of 50% FIO2). After hypoxemia, arterial O2 saturation (SaO2) declined similarly in the young and older men. MSNA (burst frequency and total minute activity) increased significantly (P < 0.05) in both groups. The magnitudes of the absolute increases in MSNA and the delta MSNA/delta SaO2 were not significantly different in the young and older men; however, because of higher normoxic baseline levels, the percentage increases in burst frequency were smaller (P = 0.02) and those for total minute activity tended to be smaller (P = 0.11) in the older men. Arterial blood pressure increased modestly (P < 0.05) and similarly in both groups, although the older men demonstrated a smaller increase in heart rate. After hyperoxemia [corrected], SaO2 increased and MSNA decreased (both P < 0.05) similarly in the young and older men. Arterial blood pressure did not change significantly from normoxic control levels in either group; however, a small (P < 0.05) reduction in heart rate was observed in both groups. In conclusion, aging does not obviously influence the regulation of absolute levels of MSNA or arterial blood pressure during alterations in systemic O2 levels in healthy men, although older men demonstrate a smaller percentage increase in MSNA from their elevated baseline levels, as well as an attenuated tachycardia in response to acute hypoxemia. As such, the present results are consistent with our previous findings on aging and sympathocirculatory control during other types of acute stress in humans.
K P Davy; P P Jones; D R Seals
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  273     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1997 Aug 
Date Detail:
Created Date:  1997-09-25     Completed Date:  1997-09-25     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:  R690-5     Citation Subset:  IM; S    
Department of Kinesiology, University of Colorado, Boulder 80309, USA.
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MeSH Terms
Adaptation, Physiological*
Aging / physiology*
Anoxia / physiopathology
Hyperoxia / blood,  physiopathology
Middle Aged
Muscle, Skeletal / innervation
Oxygen / blood*
Reference Values
Sympathetic Nervous System / physiology*
Grant Support
Reg. No./Substance:
Erratum In:
Am J Physiol 1998 Mar;274(3 Pt 2):R576

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

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