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Thermoregulatory reflex control of cutaneous vasodilation in healthy aging
Journal article   Open access   Peer reviewed

Thermoregulatory reflex control of cutaneous vasodilation in healthy aging

Jody L Greaney, Anna E Stanhewicz, S. Tony Wolf and W. Larry Kenney
Temperature (Austin), Vol.8(2), pp.176-187
2021
DOI: 10.1080/23328940.2020.1832950
PMCID: PMC8098076
PMID: 33997116
url
https://doi.org/10.1080/23328940.2020.1832950View
Published (Version of record) Open Access

Abstract

Reflex cutaneous vasodilation during heating is attenuated in healthy human aging secondary to blunted increases in efferent skin sympathetic nervous system activity (SSNA) and reductions in end-organ sensitivity. Whether age-related alterations in the mean body temperature ( b ) threshold for increasing SSNA and/or the sensitivity of responses are evident with aging have not been examined. We tested the hypotheses that the T b threshold for SSNA and cutaneous vascular conductance (CVC) would be increased, but the sensitivity would be reduced, with aging. Reflex vasodilation was induced in 13 young (23 ± 3 y) and 13 older (67 ± 7 y) adults using a water-perfused suit to systematically increase mean skin and esophageal temperatures. SSNA (peroneal microneurography) and red cell flux (laser Doppler flowmetry) in the innervated dermatome were continuously measured. SSNA was normalized to baseline; CVC was normalized as a percentage of maximal CVC. Baseline b was lower in older adults (36.0 ± 0.4°C vs 36.4 ± 0.3°C; p = 0.005). During passive heating, the ∆ b thresholds for increasing SSNA and CVC were greater (1.3 ± 0.4°C vs 0.9 ± 0.3°C; p = 0.007 and 1.3 ± 0.4°C vs 0.8 ± 0.3°C; p = 0.002, respectively) in older adults. The slope of the relation between both SSNA (0.31 ± 0.23 vs 0.13 ± 0.10 V⋅s⋅°C −1 ; p = 0.01) and CVC (87.5 ± 50.1 vs 32.4 ± 18.1%max⋅°C −1 ; p = 0.002) vs b was lower in older adults. The relative b threshold for activation of SSNA and the initiation of reflex cutaneous vasodilation is higher in older adults, and once activated, the sensitivity of both responses is diminished, supporting the concept that the efferent component of the thermoregulatory reflex arc is impaired in healthy aging. Abbreviations: CI: confidence interval; CVC: cutaneous vascular conductance; SSNA: skin sympathetic nervous system activity; b : mean body temperature; T es : esophageal temperature; sk : mean skin temperature.
 skin blood flow Passive heat stress microneurography skin sympathetic nervous system activity (SSNA) onset threshold

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