Absence of arterial baroreflex modulation of skin sympathetic activity and sweat rate during whole-body heating in humans
Prior findings suggest that baroreflexes are capable of modulating skin blood flow, but the effects of baroreceptor loading/unloading on sweating are less clear. Therefore, this project tested the hypothesis that pharmacologically induced alterations in arterial blood pressure in heated humans would...
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Published in: | The Journal of physiology 2001-10, Vol.536 (2), p.615-623 |
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Main Authors: | , , |
Format: | Article |
Language: | eng |
Subjects: | |
Online Access: | Get full text |
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Summary: | Prior findings suggest that baroreflexes are capable of modulating skin blood flow, but the effects of baroreceptor loading/unloading
on sweating are less clear. Therefore, this project tested the hypothesis that pharmacologically induced alterations in arterial
blood pressure in heated humans would lead to baroreflex-mediated changes in both skin sympathetic nerve activity (SSNA) and
sweat rate.
In seven subjects mean arterial blood pressure was lowered (â8 mmHg) and then raised (â13 mmHg) by bolus injections of sodium
nitroprusside and phenylephrine, respectively. Moreover, in a separate protocol, arterial blood pressure was reduced via steady-state
administration of sodium nitroprusside. In both normothermia and heat-stress conditions the following responses were monitored:
sublingual and mean skin temperatures, heart rate, beat-by-beat blood pressure, skin blood flow (laser-Doppler flowmetry),
local sweat rate and SSNA (microneurography from peroneal nerve).
Whole-body heating increased skin and sublingual temperatures, heart rate, cutaneous blood flow, sweat rate and SSNA, but
did not change arterial blood pressure. Heart rate was significantly elevated (from 74 ± 3 to 92 ± 4 beats min â1 ; P < 0.001) during bolus sodium nitroprusside-induced reductions in blood pressure, and significantly reduced (from 92 ± 4 to
68 ± 4 beats min â1 ; P < 0.001) during bolus phenylephrine-induced elevations in blood pressure, thereby demonstrating normal baroreflex function
in these subjects.
Neither SSNA nor sweat rate was altered by rapid (bolus infusion) or sustained (steady-state infusion) changes in blood pressure
regardless of the thermal condition.
These data suggest that SSNA and sweat rate are not modulated by arterial baroreflexes in normothermic or moderately heated
individuals. |
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ISSN: | 0022-3751 1469-7793 |