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BAROREFLEX CONTROL OF MUSCLE SYMPATHETIC NERVE ACTIVITY AS A MECHANISM FOR PERSISTENT SYMPATHOEXCITATION FOLLOWING ACUTE HYPOXIA IN HUMANS.
MedLine Citation:
PMID:  21957156     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
This study tested the hypothesis that acute isocapnic hypoxia results in persistent resetting of the baroreflex to higher levels of muscle sympathetic nerve activity (MSNA), which outlasts the hypoxic stimulus. Cardiorespiratory measures were recorded in humans (26 ± 1 yrs; n = 14; 3 female) during baseline, exposure to 20 min of isocapnic hypoxia, and for 5 min following termination of hypoxia. The spontaneous baroreflex threshold technique was used to determine the change in baroreflex function during, and following 20 min of isocapnic hypoxia (oxyhemoglobin saturation = 80%). From the spontaneous baroreflex analysis, the linear regression between diastolic blood pressure (DBP) and sympathetic burst occurrence, the T50 (DBP with a 50% likelihood of a burst occurring), and DBP error signal (DBP minus the T50) provide indexes of baroreflex function. MSNA and DBP increased in hypoxia and remained elevated during post-hypoxia relative to baseline (P < 0.05). The DBP error signal became progressively less negative (i.e. smaller difference between DBP and T50) in the hypoxia and post-hypoxia periods (baseline: -3.9 ± 0.8 mmHg; hypoxia: -1.4 ± 0.6 mmHg; post-hypoxia: 0.2 ± 0.6 mmHg; P < 0.05). Hypoxia caused no change in the slope of the baroreflex stimulus-response curve; however there was a shift toward higher pressures that favoured elevations in MSNA, which persisted post-hypoxia. Our results indicate that there is a resetting of the baroreflex in hypoxia that outlasts the stimulus, and provide further explanation for the complex control of MSNA following acute hypoxia.
Authors:
Jordan S Querido; Erica A Wehrwein; Emma Charlotte Jane Hart; Nisha Charkoudian; William R Henderson; Andrew William Sheel
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-9-28
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  -     ISSN:  1522-1490     ISO Abbreviation:  -     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-9-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
1The University of British Columbia.
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