Document Detail

Carotid baroreceptor reflexes in humans during orthostatic stress.
MedLine Citation:
PMID:  11571497     Owner:  NLM     Status:  MEDLINE    
Orthostatic stress, including standing, head-up tilting and lower body suction, results in increases in peripheral vascular resistance but little or no change in mean arterial pressure. This study was undertaken to determine whether the sensitivity of the carotid baroreceptor reflex was enhanced during conditions of decreased venous return. We studied eight healthy subjects and determined responses of pulse interval (ECG) and forearm vascular resistance (mean finger blood pressure divided by Doppler estimate of brachial artery blood velocity) to graded increases and decreases in carotid transmural pressure, effected by a neck suction/pressure device. Responses were determined with and without the application of lower body negative pressure (LBNP) at -40 mmHg. Stimulus-response curves were determined as the responses to graded neck pressure changes and the differential of this provided estimates of reflex sensitivity. Changes in carotid transmural pressure caused graded changes in R-R interval and vascular resistance. The cardiac responses were unaffected by LBNP. Vascular resistance responses, however, were significantly enhanced during LBNP and the peak gain of the reflex was increased from 1.2 +/- 0.3 (mean +/- S.E.M.) to 2.2 +/- 0.3 units (P < 0.05). The increased baroreflex gain may contribute to maintenance of blood pressure during orthostatic stress and limit the pressure decreases during prolonged periods of such stress.
V L Cooper; R Hainsworth
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Experimental physiology     Volume:  86     ISSN:  0958-0670     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2001 Sep 
Date Detail:
Created Date:  2001-09-25     Completed Date:  2002-02-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  677-81     Citation Subset:  IM; S    
Institute for Cardiovascular Research, University of Leeds, Leeds LS2 9JT, UK.
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MeSH Terms
Baroreflex / physiology*
Blood Pressure / physiology
Carotid Arteries / innervation,  physiology*
Heart Rate / physiology
Laser-Doppler Flowmetry
Lower Body Negative Pressure
Middle Aged
Vascular Resistance / physiology

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