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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.

Tymko, MM and Tremblay, JC and Steinback, CD and Moore, JP and Hansen, AB and Patrician, A and Howe, CA and Hoiland, RL and Green, DJ and Ainslie, PN (2017) UBC-Nepal Expedition: Acute alterations in sympathetic nervous activity do not influence brachial artery endothelial function at sea-level and high-altitude. Journal of Applied Physiology (1985). ISSN 8750-7587

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Abstract

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 to 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 (344m) and HA (5050m) 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 (electrodcardiogram), 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 to 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.

Item Type: Article
Uncontrolled Keywords: 06 Biological Sciences, 11 Medical And Health Sciences
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Publisher: Amercian Physiological Society
Related URLs:
Date Deposited: 27 Sep 2017 11:02
Last Modified: 27 Sep 2017 11:02
DOI or Identification number: 10.1152/japplphysiol.00583.2017
URI: http://researchonline.ljmu.ac.uk/id/eprint/7221

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