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Baroreflex control of muscle sympathetic nerve activity (MSNA) as a mechanism for persistent sympathoexcitation following acute hypoxia
Author(s) -
Querido Jordan,
Wehrwein Erica A,
Hart Emma C,
Charkoudian Nisha,
Sheel Andrew William
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1110.2
Subject(s) - microneurography , baroreflex , hypoxia (environmental) , blood pressure , medicine , heart rate , diastole , anesthesia , cardiology , stimulus (psychology) , endocrinology , psychology , chemistry , oxygen , organic chemistry , psychotherapist
Acute hypoxia elevates MSNA; however, the mechanisms are unclear. MSNA is under strong baroreflex control, and previous research indicates that the baroreflex is reset to higher blood pressures in hypoxia. The purpose of this study was to test the hypothesis that resetting in the baroreflex during hypoxia persists following termination of the hypoxic stimulus, causing long‐lasting elevations in MSNA. Healthy subjects (n = 14, 3 female) laid recumbent for 45 min: 15 min baseline, 20 min isocapnic hypoxia (SaO 2 = 80%), 10 min normoxic post‐hypoxia. Peroneal MSNA was continuously recorded with microneurography. Hypoxia resulted in an increase in MSNA (~40%, P <0.05) and diastolic blood pressure (DBP, P <0.05) which persisted in normoxic post‐hypoxia. The ‘T50’ value (DBP that was associated with a 50% likelihood of a MSNA occurring), and the ‘error signal’ for burst activation (T50 minus DBP) were calculated in each condition. Using spontaneous baroreflex threshold analysis, the slope relating MSNA and DBP was not different between conditions; however, the ‘error signal’ progressively increased with hypoxia and further during normoxic post‐hypoxia (baseline: −3.9 +/− 0.8 mmHg; hypoxia: −1.4 +/− 0.6 mmHg; post‐hypoxia: +0.2 +/− 0.6 mmHg, P <0.05). We conclude that hypoxia results in a prolonged reduction in the error signal allowing for a persistent increase in MSNA compared to baseline. Research support: HSFC, MSFHR, CSN, CIHR