Sex differences in the sympathetic neurocirculatory responses to chemoreflex activation

• Published in: The Journal of physiology 2022-06, Vol.600 (11), p.2669-2689
• Main Authors: Sayegh, Ana Luiza C., Fan, Jui‐Lin, Vianna, Lauro C., Dawes, Mathew, Paton, Julian F. R., Fisher, James P.
• Format: Article
• Language: English
• Subjects: Blood pressure; Carbon dioxide; Cardiovascular; central chemoreflex; Chemoreception (internal); Gender differences; Hyperoxia; Hypoxia; Mechanical ventilation; Microneurography; neurovascular transduction; peripheral chemoreflex; Sex differences; Sympathetic nerves; sympathetic nervous system; Ventilation; Women; Young adults
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/JP282327

The purpose of this study was to determine whether there are sex differences in the cardiorespiratory and sympathetic neurocirculatory responses to central, peripheral, and combined central and peripheral chemoreflex activation. Ten women (29 ± 6 years, 22.8 ± 2.4 kg/m2: mean ± SD) and 10 men (30 ± 7 years, 24.8 ± 3.2 kg/m2) undertook randomized 5 min breathing trials of: room air (eucapnia), isocapnic hypoxia (10% oxygen (O2); peripheral chemoreflex activation), hypercapnic hyperoxia (7% carbon dioxide (CO2), 50% O2; central chemoreflex activation) and hypercapnic hypoxia (7% CO2, 10% O2; central and peripheral chemoreflex activation). Control trials of isocapnic hyperoxia (peripheral chemoreflex inhibition) and hypocapnic hyperoxia (central and peripheral chemoreflex inhibition) were also included. Muscle sympathetic nerve activity (MSNA; microneurography), mean arterial pressure (MAP; finger photoplethysmography) and minute ventilation (V̇$\dot{\rm{V}}$E; pneumotachometer) were measured. Total MSNA (P = 1.000 and P = 0.616), MAP (P = 0.265) and V̇$\dot{\rm{V}}$E (P = 0.587 and P = 0.472) were not different in men and women during eucapnia and during isocapnic hypoxia. Women exhibited attenuated increases in V̇$\dot{\rm{V}}$E during hypercapnic hyperoxia (27.3 ± 6.3 vs. 39.5 ± 7.5 l/min, P