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Effects of graded LBNP on MSNA and interstitial norepinephrineExposure to lower body negative pressure (LBNP) leads to an increased activation of the sympathetic nervous system (SNS) and an increase in muscle sympathetic nerve activity (MSNA). In this study, we examined the relationship between MSNA and interstitial norepinephrine (NE(i)) concentrations during LBNP. Twelve healthy volunteers were studied (26 +/- 6 yr). Simultaneous MSNA and microdialysis data were collected in six of these subjects. Measurements of MSNA (microneurography) and NE(i) (microdialysis, vastus lateralis) were performed at rest and then during an incremental LBNP paradigm (-10, -30, and -50 mmHg). MSNA rose as a function of LBNP (P < 0.001, n = 12). The plasma norepinephrine (NE(p)) concentration was 0.9 +/- 0.1 nmol/l at rest (n = 12). NE(i) measured in six subjects rose from 5.2 +/- 0.8 nmol/l at rest to 17.0 +/- 1.7 nmol/l at -50 mmHg (P < 0.001). Of note, the rise in NE(p) with LBNP was considerably less compared with the changes in NE(i) (Delta21 +/- 6% vs. Delta197 +/- 52%, n = 6, P < 0.015). MSNA and NE(i) showed a significant linear relationship (r = 0.721, P < 0.004). Activation of the SNS increased MSNA and NE(i) levels. The magnitude of the NE(i) increase was far greater than that seen for NE(p) suggesting that NE movement into the circulation decreases with baroreceptor unloading.
Document ID
20040088036
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Khan, Mazhar H.
(The Pennsylvania State University College of Medicine and The Milton S. Hershey Medical Center Hershey, PA 17033, United States)
Sinoway, Lawrence I.
MacLean, David A.
Date Acquired
August 21, 2013
Publication Date
November 1, 2002
Publication Information
Publication: American journal of physiology. Heart and circulatory physiology
Volume: 283
Issue: 5
ISSN: 0363-6135
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: R01 HL 60800
CONTRACT_GRANT: M01 RR 10732
CONTRACT_GRANT: R01 AG 12227
CONTRACT_GRANT: K24 HL 04011
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cardiopulmonary
Non-NASA Center

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