TY - JOUR
T1 - Muscle sympathetic nerve activity during lower body negative pressure is accentuated in heat-stressed humans
AU - Cui, Jian
AU - Wilson, Thad E.
AU - Crandall, Craig G.
PY - 2004/6
Y1 - 2004/6
N2 - The purpose of this project was to test the hypothesis that increases in muscle sympathetic nerve activity (MSNA) during an orthostatic challenge is attenuated in heat-stressed individuals. To accomplish this objective, MSNA was measured during graded lower body negative pressure (LBNP) in nine subjects under normothermic and heat-stressed conditions. Progressive LBNP was applied at -3, -6, -9, -12, -15, -18, -21, and -40 mmHg for 2 min per stage. Whole body heating caused significant increases in sublingual temperature, skin blood flow, sweat rate, heart rate, and MSNA (all P < 0.05) but not in mean arterial blood pressure (P > 0.05). Progressive LBNP induced significant increases in MSNA in both thermal conditions. However, during the heat stress trial, increases in MSNA at LBNP levels higher than -9 mmHg were greater compared with during the same LBNP levels in normothermia (all P < 0.05). These data suggest that the increase in MSNA to orthostatic stress is not attenuated but rather accentuated in heat-stressed humans.
AB - The purpose of this project was to test the hypothesis that increases in muscle sympathetic nerve activity (MSNA) during an orthostatic challenge is attenuated in heat-stressed individuals. To accomplish this objective, MSNA was measured during graded lower body negative pressure (LBNP) in nine subjects under normothermic and heat-stressed conditions. Progressive LBNP was applied at -3, -6, -9, -12, -15, -18, -21, and -40 mmHg for 2 min per stage. Whole body heating caused significant increases in sublingual temperature, skin blood flow, sweat rate, heart rate, and MSNA (all P < 0.05) but not in mean arterial blood pressure (P > 0.05). Progressive LBNP induced significant increases in MSNA in both thermal conditions. However, during the heat stress trial, increases in MSNA at LBNP levels higher than -9 mmHg were greater compared with during the same LBNP levels in normothermia (all P < 0.05). These data suggest that the increase in MSNA to orthostatic stress is not attenuated but rather accentuated in heat-stressed humans.
KW - Autonomic nervous system
KW - Baroreflexes
KW - Hyperthermia
KW - Orthostasis
KW - Vasomotor
UR - https://www.scopus.com/pages/publications/2442651616
UR - https://www.scopus.com/inward/citedby.url?scp=2442651616&partnerID=8YFLogxK
U2 - 10.1152/japplphysiol.00717.2003
DO - 10.1152/japplphysiol.00717.2003
M3 - Article
C2 - 14978004
AN - SCOPUS:2442651616
SN - 8750-7587
VL - 96
SP - 2103
EP - 2108
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 6
ER -