Influence of sex on carotid baroreflex control of muscle sympathetic nerve activity during hypo‐ and hypertensive stimuli in humans

The arterial baroreflex is critical for defending against both falls and rises in arterial blood pressure (BP). Limited studies have examined sex related differences in baroreflex control of muscle sympathetic nerve activity (MSNA). Furthermore, studies have mainly focused on overall baroreflex control and have not distinguished between MSNA responses to hypotensive and hypertensive stimuli. Therefore, in 8 men and 5 women, MSNA and BP were measured during 5s pulses of neck pressure (NP, +40 Torr) and neck suction (NS, −60 Torr) to simulate carotid sinus hypotension and hypertension, respectively. Resting BP was similar between sexes, while MSNA burst incidence was significantly lower in women. In response to NP, increases in MSNA total activity were significantly greater in men (Δ+198±31% men vs. Δ+102±22% women; P<0.05), whereas MSNA responses to NS appeared similar between groups (Δ−48±12% men vs. Δ−73±13% women; P>0.05). Interestingly, BP responses to NP and NS were not different between men and women. These preliminary findings suggest that young men and women exhibit comparable sympathoinhibition in response to hypertensive stimuli. However, similar BP responses but the attenuated sympathoexcitatory response to a hypotensive stimuli in women, suggests inherent sex differences in the mechanisms by which the arterial baroreflex regulates BP. Supported by R01HL093167