Baroreflex control of muscle sympathetic nerve activity as a mechanism for persistent sympathoexcitation following acute hypoxia in humans

Jordan S Querido, Erica A Wehrwein, Emma C Hart, Nisha Charkoudian, William R Henderson, A William Sheel

Research output: Contribution to journalArticle (Academic Journal)peer-review

27 Citations (Scopus)

Abstract

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 yr; n = 14; 3 women) 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 posthypoxia 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 posthypoxia periods (baseline: -3.9 ± 0.8 mmHg; hypoxia: -1.4 ± 0.6 mmHg; posthypoxia: 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 favored elevations in MSNA, which persisted posthypoxia. 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.

Translated title of the contributionBAROREFLEX CONTROL OF MUSCLE SYMPATHETIC NERVE ACTIVITY AS A MECHANISM FOR PERSISTENT SYMPATHOEXCITATION FOLLOWING ACUTE HYPOXIA IN HUMANS
Original languageEnglish
Pages (from-to)R1779-85
JournalAJP - Regulatory, Integrative and Comparative Physiology
Volume301
Issue number6
DOIs
Publication statusPublished - Dec 2011

Bibliographical note

Other: Epub ahead of print

Keywords

  • Adaptation, Physiological
  • Adult
  • Anoxia
  • Baroreflex
  • Blood Pressure
  • Female
  • Heart Rate
  • Humans
  • Male
  • Muscle, Skeletal
  • Oxygen Consumption
  • Sympathetic Nervous System

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