|
|
||||||||
NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and the University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
Submitted 10 January 2005 ; accepted in final form 4 March 2005
We tested the hypothesis that women have blunted sympathetic neural responses to orthostatic stress compared with men, which may be elicited under hypovolemic conditions. Muscle sympathetic nerve activity (MSNA) and hemodynamics were measured in eight healthy young women and seven men in supine position and during 6 min of 60° head-up tilt (HUT) under normovolemic and hypovolemic conditions (randomly), with
4-wk interval. Acute hypovolemia was produced by diuretic (furosemide) administration
2 h before testing. Orthostatic tolerance was determined by progressive lower body negative pressure to presyncope. We found that furosemide produced an
13% reduction in plasma volume, causing a similar increase in supine MSNA in men and women (mean ± SD of 5 ± 7 vs. 6 ± 5 bursts/min; P = 0.895). MSNA increased during HUT and was greater in the hypovolemic than in the normovolemic condition (32 ± 6 bursts/min in normovolemia vs. 44 ± 15 bursts/min in hypovolemia in men, P = 0.055; 35 ± 9 vs. 45 ± 8 bursts/min in women, P < 0.001); these responses were not different between the genders (gender effect: P = 0.832 and 0.814 in normovolemia and hypovolemia, respectively). Total peripheral resistance increased proportionately with increases in MSNA during HUT; these responses were similar between the genders. However, systolic blood pressure was lower, whereas diastolic blood pressure was similar in women compared with men during HUT, which was associated with a smaller stroke volume or stroke index. Orthostatic tolerance was lower in women, especially under hypovolemic conditions. These results indicate that men and women have comparable sympathetic neural responses during orthostatic stress under normovolemic and hypovolemic conditions. The lower orthostatic tolerance in women is predominantly because of a smaller stroke volume, presumably due to less cardiac filling during orthostasis, especially under hypovolemic conditions, which may overwhelm the vasomotor reserve available for vasoconstriction or precipitate neurally mediated sympathetic withdrawal and syncope.
muscle sympathetic nerve activity; vascular resistance; arterial pressure; head-up tilt
This article has been cited by other articles:
![]() |
T. A. Dorfman, B. D. Rosen, M. A. Perhonen, T. Tillery, R. McColl, R. M. Peshock, and B. D. Levine Diastolic suction is impaired by bed rest: MRI tagging studies of diastolic untwisting J Appl Physiol, April 1, 2008; 104(4): 1037 - 1044. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Edgell, K. A. Zuj, D. K. Greaves, J. K. Shoemaker, M.-A. Custaud, P. Kerbeci, P. Arbeille, and R. L. Hughson WISE-2005: adrenergic responses of women following 56-days, 6{degrees} head-down bed rest with or without exercise countermeasures Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2007; 293(6): R2343 - R2352. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. C. Tuday and D. E. Berkowitz Microgravity and cardiac atrophy: no sex discrimination J Appl Physiol, July 1, 2007; 103(1): 1 - 2. [Full Text] [PDF] |
||||
![]() |
T. A. Dorfman, B. D. Levine, T. Tillery, R. M. Peshock, J. L. Hastings, S. M. Schneider, B. R. Macias, G. Biolo, and A. R. Hargens Cardiac atrophy in women following bed rest J Appl Physiol, July 1, 2007; 103(1): 8 - 16. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. Taneja, C. Moran, M. S. Medow, J. L. Glover, L. D. Montgomery, and J. M. Stewart Differential effects of lower body negative pressure and upright tilt on splanchnic blood volume Am J Physiol Heart Circ Physiol, March 1, 2007; 292(3): H1420 - H1426. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Lindenberger and T. Lanne Sex-related effects on venous compliance and capillary filtration in the lower limb Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R852 - R859. [Abstract] [Full Text] [PDF] |
||||
![]() |
Q. Fu, R. P. Shook, K. Okazaki, J. L. Hastings, S. Shibata, C. L. Conner, M. D. Palmer, and B. D. Levine Vasomotor sympathetic neural control is maintained during sustained upright posture in humans J. Physiol., December 1, 2006; 577(2): 679 - 687. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. A. Lipsitz, I. Iloputaife, M. Gagnon, D. K. Kiely, and J. M. Serrador Enhanced Vasoreactivity and Its Response to Antihypertensive Therapy in Hypertensive Elderly Women Hypertension, March 1, 2006; 47(3): 377 - 383. [Abstract] [Full Text] [PDF] |
||||
![]() |
N Charkoudian, M. J Joyner, C. P Johnson, J. H Eisenach, N. M Dietz, and B. G Wallin Balance between cardiac output and sympathetic nerve activity in resting humans: role in arterial pressure regulation J. Physiol., October 1, 2005; 568(1): 315 - 321. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |