The arterial baroreflex plays a critical role in the beat-to-beat regulation of arterial
blood pressure (BP) primarily via reflex modulation of sympathetic nerve activity
and vascular conductance. Limited studies focusing on sex differences have reported
similar sympathetic baroreflex sensitivity at rest between young normotensive men
and women. These data are interesting given recent evidence suggesting that resting
arterial BP is differentially regulated in young men and women. Importantly, while
the overall baroreflex control of muscle sympathetic nerve activity is critical, the
actual vascular response evoked by baroreflex-mediated alterations in sympathetic
nerve activity is essential for the ultimate control of BP. Consequently, we sought
to examine possible sex-related differences in arterial baroreflex control of leg
vascular conductance (LVC) in humans. To begin to address this question, mean BP,
femoral blood flow, and LVC responses to carotid baroreflex activation were characterized
in five young men and six young women at rest using 5 s pulses of neck suction (−60 Torr). In response to neck suction, increases in LVC were significantly greater in
men compared to women (+20±5% men vs. +5±3% women, P<0.05). Likewise, men exhibited greater increases in femoral blood flow to neck suction
when compared to women (+13±4% men vs. +1±4% women, P<0.05). Interestingly, despite the blunted increase in LVC, mean BP responses to neck
suction were significantly greater in women compared to men. These preliminary findings
suggest that the ability of the carotid baroreflex to regulate vascular conductance
appears to be reduced in young women compared to men. The lack of a concomitant reduction
in carotid baroreflex mediated BP responses in women suggests inherent sex differences
in the mechanisms by which the arterial baroreflex regulates BP.
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© 2010 Published by Elsevier Inc.