Highs and lows of sympathetic neurocardiovascular transduction: influence of altitude acclimatization and adaptation

Stembridge, M.; Lawley, J.S.; Berthelsen, L.F.; Meah, V.L.; Ainslie, P.N.; Steinback, C.D.; Willie, C.K.; Simpson, L.L.; Moore, J.P.; Steele, A.R.; Vanden Berg, E.R.; Figueroa-Mujíca, R.J.; Gasho, C.; Busch, S.A.; Tymko, M.M.; Vizcardo-Galindo, G.; Fraser, G.M.; Villafuerte, Francisco C.

dc.contributor.author	Berthelsen, L.F.
dc.contributor.author	Fraser, G.M.
dc.contributor.author	Simpson, L.L.
dc.contributor.author	Vanden Berg, E.R.
dc.contributor.author	Busch, S.A.
dc.contributor.author	Steele, A.R.
dc.contributor.author	Meah, V.L.
dc.contributor.author	Lawley, J.S.
dc.contributor.author	Figueroa-Mujíca, R.J.
dc.contributor.author	Vizcardo-Galindo, G.
dc.contributor.author	Villafuerte, Francisco C.
dc.contributor.author	Gasho, C.
dc.contributor.author	Willie, C.K.
dc.contributor.author	Tymko, M.M.
dc.contributor.author	Ainslie, P.N.
dc.contributor.author	Stembridge, M.
dc.contributor.author	Moore, J.P.
dc.contributor.author	Steinback, C.D.
dc.date.accessioned	2020-12-14T16:06:09Z
dc.date.available	2020-12-14T16:06:09Z
dc.date.issued	2020
dc.identifier.uri	https://hdl.handle.net/20.500.12866/8668
dc.description.abstract	High-altitude (>2,500 m) exposure results in increased muscle sympathetic nervous activity (MSNA) in acclimatizing lowlanders. However, little is known about how altitude affects MSNA in indigenous high-altitude populations. Additionally, the relationship between MSNA and blood pressure regulation (i.e., neurovascular transduction) at high-altitude is unclear. We sought to determine 1) how high-altitude effects neurocardiovascular transduction and 2) whether differences exist in neurocardiovascular transduction between low- and high-altitude populations. Measurements of MSNA (microneurography), mean arterial blood pressure (MAP; finger photoplethysmography), and heart rate (electrocardiogram) were collected in 1) lowlanders (n = 14) at low (344 m) and high altitude (5,050 m), 2) Sherpa highlanders (n = 8; 5,050 m), and 3) Andean (with and without excessive erythrocytosis) highlanders (n = 15; 4,300 m). Cardiovascular responses to MSNA burst sequences (i.e., singlet, couplet, triplet, and quadruplet) were quantified using custom software (coded in MATLAB, v.2015b). Slopes were generated for each individual based on peak responses and normalized total MSNA. High altitude reduced neurocardiovascular transduction in lowlanders (MAP slope: high altitude, 0.0075 ± 0.0060 vs. low altitude, 0.0134 ± 0.080; P = 0.03). Transduction was elevated in Sherpa (MAP slope, 0.012 ± 0.007) compared with Andeans (0.003 ± 0.002, P = 0.001). MAP transduction was not statistically different between acclimatizing lowlanders and Sherpa (MAP slope, P = 0.08) or Andeans (MAP slope, P = 0.07). When resting MSNA is accounted for (ANCOVA), transduction was inversely related to basal MSNA (bursts/minute) independent of population (RRI, r = 0.578 P < 0.001; MAP, r = -0.627, P < 0.0001). Our results demonstrate that transduction is blunted in individuals with higher basal MSNA, suggesting that blunted neurocardiovascular transduction is a physiological adaptation to elevated MSNA rather than an effect or adaptation specific to chronic hypoxic exposure.NEW & NOTEWORTHY This study has identified that sympathetically mediated blood pressure regulation is reduced following ascent to high-altitude. Additionally, we show that high altitude Andean natives have reduced blood pressure responsiveness to sympathetic nervous activity (SNA) compared with Nepalese Sherpa. However, basal sympathetic activity is inversely related to the magnitude of SNA-mediated fluctuations in blood pressure regardless of population or condition. These data set a foundation to explore more precise mechanisms of blood pressure control under conditions of persistent sympathetic activation and hypoxia.	en_US
dc.language.iso	eng
dc.publisher	American Physiological Society
dc.relation.ispartofseries	American Journal of Physiology - Heart and Circulatory Physiology
dc.rights	info:eu-repo/semantics/restrictedAccess
dc.subject	Altitude	en_US
dc.subject	Hypoxia	en_US
dc.subject	Neurocardiovascular Transduction	en_US
dc.subject	Sympathetic Nerve Activity	en_US
dc.title	Highs and lows of sympathetic neurocardiovascular transduction: influence of altitude acclimatization and adaptation	en_US
dc.type	info:eu-repo/semantics/article
dc.identifier.doi	https://doi.org/10.1152/ajpheart.00364.2020
dc.subject.ocde	https://purl.org/pe-repo/ocde/ford#3.01.08
dc.subject.ocde	https://purl.org/pe-repo/ocde/ford#3.02.04
dc.relation.issn	1522-1539