HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 289/5/R1440    most recent 00356.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Foley, C. M. Articles by Heesch, C. M. Search for Related Content PubMed PubMed Citation Articles by Foley, C. M. Articles by Heesch, C. M.

NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Hindlimb unloading and female gender attenuate baroreflex-mediated sympathoexcitation

¹Department of Biomedical Sciences, ²Department of Medical Pharmacology and Physiology, and ³Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, Missouri

Submitted 20 May 2005 ; accepted in final form 20 July 2005

Exposure to a period of microgravity or bed rest produces several physiological adaptations. These changes, which include an increased incidence of orthostatic intolerance, have an impact when people return to a 1G environment or resume an upright posture. Compared with males, females appear more susceptible to orthostatic intolerance after exposure to real or simulated microgravity. Decreased arterial baroreflex compensation may contribute to orthostatic intolerance. We hypothesized that female rats would exhibit a greater reduction in arterial baroreflex function after hindlimb unloading (HU) compared with male rats. Mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded in conscious animals after 13–15 days of HU. Baseline HR was elevated in female rats, and HU increased HR in both genders. Consistent with previous results in males, baroreflex-mediated activation of RSNA was blunted by HU in both genders. Maximum RSNA in response to decreases in MAP was reduced by HU (male control 513 ± 42%, n = 11; male HU 346 ± 38%, n = 13; female control 359 ± 44%, n = 10; female HU 260 ± 43%, n = 10). Maximum baroreflex increase in RSNA was lower in females compared with males in both control and HU rats. Both female gender and HU attenuated baroreflex-mediated increases in sympathetic activity. The combined effects of HU and gender resulted in reduced baroreflex sympathetic reserve in females compared with males and could contribute to the greater incidence of orthostatic intolerance in females after exposure to spaceflight or bed rest.

simulated microgravity; sympathetic nervous system; bed rest; deconditioning; hindlimb unweighting

This article has been cited by other articles:

				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]

				F. W. Booth and S. J. Lees Fundamental questions about genes, inactivity, and chronic diseases Physiol Genomics, January 17, 2007; 28(2): 146 - 157. [Abstract] [Full Text] [PDF]

				R. Kanbar, V. Orea, C. Barres, and C. Julien Baroreflex control of renal sympathetic nerve activity during air-jet stress in rats Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R362 - R367. [Abstract] [Full Text] [PDF]

				P. J. Mueller, M. J. Sullivan, R. R. Grindstaff, J. T. Cunningham, and E. M. Hasser Regulation of plasma vasopressin and renin activity in conscious hindlimb-unloaded rats Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2006; 291(1): R46 - R52. [Abstract] [Full Text] [PDF]