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UBC-Nepal Expedition: acute alterations in sympathetic nervous activity do not influence brachial artery endothelial function at sea level and high altitude
Univ British Columbia, Sch Hlth & Exercise Sci, Ctr Heart Lung & Vasc Hlth, Kelowna, BC, Canada.
Queens Univ, Sch Kinesiol & Hlth Studies, Cardiovasc Stress Response Lab, Kingston, ON, Canada.ORCID iD: 0000-0002-1667-294X
Univ Alberta, Fac Phys Educ & Recreat, Edmonton, AB, Canada.
Bangor Univ, Extremes Res Grp, Sch Sport Hlth & Exercise Sci, Bangor, Gwynedd, Wales.
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2017 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 123, no 5, p. 1386-1396Article in journal (Refereed) Published
Abstract [en]

Evidence indicates that increases in sympathetic nervous activity (SNA), and acclimatization to high altitude (HA), may reduce endothelial function as assessed by brachial artery flow-mediated dilatation (FMD); however, it is unclear whether such changes in FMD are due to direct vascular constraint, or consequential altered hemodynamics (e.g., shear stress) associated with increased SNA as a consequence of exposure to HA. We hypothesized that 1) at rest, SNA would be elevated and FMD would be reduced at HA compared with sea-level (SL);and 2) at SL and HA, FMD would be reduced when SNA was acutely increased, and elevated when SNA was acutely decreased. Using a novel, randomized experimental design, brachial artery FMD was assessed at SL (344 m) and HA (5,050 m) in 14 participants during mild lower-body negative pressure (LBNP; -10 mmHg) and lower-body positive pressure (LBPP; -10 mmHg). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (Duplex ultrasound) were recorded during LBNP, control, and LBPP trials. Muscle SNA was recorded (via microneurography) in a subset of participants (n = 5). Our findings were 1) at rest, SNA was elevated (P < 0.01), and absolute FMD was reduced (P = 0.024), but relative FMD remained unaltered (P = 0.061), at HA compared with SL; and 2) despite significantly altering SNA with LBNP (+60.3 +/- 25.5%) and LBPP (-37.2 +/- 12.7%) (P < 0.01), FMD was unaltered at SL (P = 0.448) and HA (P = 0.537). These data indicate that acute and mild changes in SNA do not directly influence brachial artery FMD at SL or HA.

Place, publisher, year, edition, pages
2017. Vol. 123, no 5, p. 1386-1396
Keyword [en]
sympathetic nervous activity, lower-body negative pressure, lower-body positive pressure, endothelial function, high altitude
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:miun:diva-32563DOI: 10.1152/japplphysiol.00583.2017ISI: 000416597900039OAI: oai:DiVA.org:miun-32563DiVA: diva2:1168603
Available from: 2017-12-21 Created: 2017-12-21 Last updated: 2017-12-21Bibliographically approved

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Patrician, Alexander

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