Premium
Heat stress decreases baroreflex sensitivity during muscle metaboreceptor stimulation
Author(s) -
Cui Jian,
Shibasaki Manabu,
Davis Scott,
Low David,
Keller David,
Crandall Craig
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a571-a
Subject(s) - baroreflex , isometric exercise , heart rate , medicine , stimulation , blood pressure , anesthesia , sympathetic nervous system , cardiology
Muscle metaboreceptor stimulation increases the gain of baroreflex control of muscle sympathetic nerve activity (MSNA) in normothermic individuals. However, prolonged exercise increases both muscle and internal temperatures. To that end, this study tested the hypothesis that the effect of muscle metaboreceptor stimulation on baroreflex function will be altered when individuals are heat stressed. MSNA, blood pressure (BP, Finapres), and ECG were recoded in 11 healthy subjects. Subjects performed isometric handgrip exercise until fatigue, followed by 2.5 min of post‐exercise muscle ischemia (PEMI). During PEMI, BP was acutely reduced and then raised pharmacologically using the modified Oxford technique. This protocol was repeated 2 to 3 times during both normothermic and whole body heating (WBH, increase core temperature ~ 0.7 °C) conditions. The slope of the relationship between MSNA and BP during PEMI was less negative after WBH when compared with normothermic condition (−3.57 ± 0.31 vs −4.34 ± 0.40 units/beat/mmHg, p=0.015). Moreover, the gain of baroreflex control of heart rate during PEMI was also decreased after WBH (−0.485 ± 0.07 vs −0.797 ± 0.103 beats/mmHg, p<0.001). These data suggest that the effect of muscle metaboreceptor stimulation on baroreflex control of MSNA and heart rate is reduced when individuals are heat stressed. Supported by NIH HL‐61388, HL‐67422, and AHA 0565399U, 0635245N.