Plasma hyperosmolality attenuates skin sympathetic nerve activity during passive heat stress in humans

Daniel Gagnon, Steven A. Romero, Hai Ngo, Paula Y S Poh, Craig G. Crandall

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

In humans, plasma hyperosmolality delays the onset of sweating and cutaneous vasodilatation during heat stress. However, it remains unknown if hyperosmolality exerts this effect through a central (i.e. CNS) and/or peripheral (i.e. effector organ) modulation of thermoregulatory activity. We examined if intravenous infusion of hyperosmotic saline affects skin sympathetic nerve activity (SSNA) during whole-body passive heating in healthy humans. Furthermore, we examined if local intradermal infusion of hyperosmotic saline affects sweating and cutaneous vasodilatation during passive heating. Following intravenous infusion of either 0.9% (ISO) or 3.0% (HYPER) NaCl saline, 12 subjects were passively heated until core temperature increased by ∼0.6°C. During each condition, sweating and cutaneous vascular conductance were measured over two intradermal microdialysis probes, one perfused with ISO saline and the other with HYPER saline. Intravenous infusion of HYPER saline increased plasma osmolality (294±3 to 316±5 mOsmkg-1 H2O, P≤0.01), which remained greater than ISO throughout heating. Plasma hyperosmolality delayed the mean body temperature onset of sweating (+1.24±0.18vs. +1.60±0.18°C, P≤0.01) and cutaneous vasodilatation (+1.15±0.18vs. +1.53±0.22°C, P≤0.01), and attenuated the increase in SSNA during heating (+147±178vs. +427±281%, P≤0.01). Intradermal infusion of HYPER saline increased baseline cutaneous vascular conductance (P≤0.01), which did not increase further during the subsequent heating period (P=0.11). In contrast, intradermal infusion of HYPER saline did not affect sweating (P=0.99). These results provide direct evidence that plasma hyperosmolality exerts a central modulatory effect governing efferent thermoregulatory activity in humans.

Original languageEnglish (US)
Pages (from-to)497-506
Number of pages10
JournalJournal of Physiology
Volume594
Issue number2
DOIs
StatePublished - Jan 15 2016

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Sweating
Hot Temperature
Heating
Skin
Intravenous Infusions
Vasodilation
Blood Vessels
Microdialysis
Body Temperature
Human Activities
Osmolar Concentration
Temperature

ASJC Scopus subject areas

  • Physiology

Cite this

Plasma hyperosmolality attenuates skin sympathetic nerve activity during passive heat stress in humans. / Gagnon, Daniel; Romero, Steven A.; Ngo, Hai; Poh, Paula Y S; Crandall, Craig G.

In: Journal of Physiology, Vol. 594, No. 2, 15.01.2016, p. 497-506.

Research output: Contribution to journalArticle

Gagnon, Daniel ; Romero, Steven A. ; Ngo, Hai ; Poh, Paula Y S ; Crandall, Craig G. / Plasma hyperosmolality attenuates skin sympathetic nerve activity during passive heat stress in humans. In: Journal of Physiology. 2016 ; Vol. 594, No. 2. pp. 497-506.
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abstract = "In humans, plasma hyperosmolality delays the onset of sweating and cutaneous vasodilatation during heat stress. However, it remains unknown if hyperosmolality exerts this effect through a central (i.e. CNS) and/or peripheral (i.e. effector organ) modulation of thermoregulatory activity. We examined if intravenous infusion of hyperosmotic saline affects skin sympathetic nerve activity (SSNA) during whole-body passive heating in healthy humans. Furthermore, we examined if local intradermal infusion of hyperosmotic saline affects sweating and cutaneous vasodilatation during passive heating. Following intravenous infusion of either 0.9{\%} (ISO) or 3.0{\%} (HYPER) NaCl saline, 12 subjects were passively heated until core temperature increased by ∼0.6°C. During each condition, sweating and cutaneous vascular conductance were measured over two intradermal microdialysis probes, one perfused with ISO saline and the other with HYPER saline. Intravenous infusion of HYPER saline increased plasma osmolality (294±3 to 316±5 mOsmkg-1 H2O, P≤0.01), which remained greater than ISO throughout heating. Plasma hyperosmolality delayed the mean body temperature onset of sweating (+1.24±0.18vs. +1.60±0.18°C, P≤0.01) and cutaneous vasodilatation (+1.15±0.18vs. +1.53±0.22°C, P≤0.01), and attenuated the increase in SSNA during heating (+147±178vs. +427±281{\%}, P≤0.01). Intradermal infusion of HYPER saline increased baseline cutaneous vascular conductance (P≤0.01), which did not increase further during the subsequent heating period (P=0.11). In contrast, intradermal infusion of HYPER saline did not affect sweating (P=0.99). These results provide direct evidence that plasma hyperosmolality exerts a central modulatory effect governing efferent thermoregulatory activity in humans.",
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