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Absence of arterial baroreflex modulation of skin sympathetic activity and sweat rate during whole-body heating in humans1. 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. 2. In seven subjects mean arterial blood pressure was lowered (approximately 8 mmHg) and then raised (approximately 13 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). 3. 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 x min(-1); P < 0.001) during bolus sodium nitroprusside-induced reductions in blood pressure, and significantly reduced (from 92 +/- 4 to 68 +/- 4 beats x min(-1); P < 0.001) during bolus phenylephrine-induced elevations in blood pressure, thereby demonstrating normal baroreflex function in these subjects. 4. 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. 5. These data suggest that SSNA and sweat rate are not modulated by arterial baroreflexes in normothermic or moderately heated individuals.
Document ID
20040088728
Document Type
Reprint (Version printed in journal)
Authors
Wilson, T. E.
(Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas Dallas, TX 752315, United States)
Cui, J.
Crandall, C. G.
Date Acquired
August 21, 2013
Publication Date
October 15, 2001
Publication Information
Publication: The Journal of physiology
Volume: 536
Issue: Pt 2
ISSN: 0022-3751
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: HL-61388
CONTRACT_GRANT: HL-10488
Distribution Limits
Public
Copyright
Other
Keywords
Clinical Trial
Non-NASA Center
NASA Discipline Cardiopulmonary

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