TY - JOUR
T1 - Highs and Lows of Sympathetic Neuro-cardiovascular Transduction: Influence of Altitude Acclimatization and Adaptation
T2 - Phenotypic differences in neuro-cardiovascular transduction
AU - Berthelsen, Lindsey F
AU - Fraser, Graham M.
AU - Simpson, Lydia
AU - Vanden Berg, Emily R
AU - Busch, Stephen A
AU - Steele, Andrew R
AU - Meah, Victoria L
AU - Lawley, Justin S
AU - Figueroa- Mujica, Romulo J
AU - Vizcardo-Galindo, Gustavo
AU - Villafuerte, Francisco
AU - Gasho, Chris
AU - Willie, Christopher
AU - Tymko, Michael M
AU - Ainslie, Philip N
AU - Stembridge, Mike
AU - Moore, Jonathan
AU - Steinback, Craig D
PY - 2020/12
Y1 - 2020/12
N2 - High-altitude (>2500m) 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 neuro-cardiovascular transduction and 2) whether differences exist in neuro-cardiovascular 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: I) lowlanders (n=14) at low (344m) and high-altitude (5050m), II) Sherpa highlanders (n=8; 5050m), and III) Andean (with and without excessive erythrocytosis) highlanders (n=15; 4300m). Cardiovascular responses to MSNA burst sequences (i.e. singlet, couplet, triplet, and quadruplets) were quantified using custom software (coded in MATLAB, v2015b). Slopes were generated for each individual based on peak responses and normalized total MSNA. High altitude reduced neuro-cardiovascular 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 to 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 accounting for resting MSNA (ANCOVA), transduction was inversely related to basal MSNA (bursts/min) independent of population (RRI, r= 0.578 p<0.001; MAP, r= -0.627 p<0.0001). Our results demonstrate transduction is blunted in individuals with higher basal MSNA, suggesting blunted neuro-cardiovascular transduction is a physiological adaptation to elevated MSNA rather than an effect or adaptation specific to chronic hypoxic exposure.
AB - High-altitude (>2500m) 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 neuro-cardiovascular transduction and 2) whether differences exist in neuro-cardiovascular 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: I) lowlanders (n=14) at low (344m) and high-altitude (5050m), II) Sherpa highlanders (n=8; 5050m), and III) Andean (with and without excessive erythrocytosis) highlanders (n=15; 4300m). Cardiovascular responses to MSNA burst sequences (i.e. singlet, couplet, triplet, and quadruplets) were quantified using custom software (coded in MATLAB, v2015b). Slopes were generated for each individual based on peak responses and normalized total MSNA. High altitude reduced neuro-cardiovascular 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 to 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 accounting for resting MSNA (ANCOVA), transduction was inversely related to basal MSNA (bursts/min) independent of population (RRI, r= 0.578 p<0.001; MAP, r= -0.627 p<0.0001). Our results demonstrate transduction is blunted in individuals with higher basal MSNA, suggesting blunted neuro-cardiovascular transduction is a physiological adaptation to elevated MSNA rather than an effect or adaptation specific to chronic hypoxic exposure.
U2 - 10.1152/ajpheart.00364.2020
DO - 10.1152/ajpheart.00364.2020
M3 - Article
SN - 0363-6135
VL - 319
SP - H1240-H1252
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
IS - 6
ER -