Women have lower tonic autonomic support of arterial blood pressure and less effective baroreflex buffering than men

BACKGROUND: Short-term and tonic regulation of arterial blood pressure (BP) differ in premenopausal women and men of similar age. The autonomic nervous system (ANS) plays a critical role in BP regulation. METHODS AND RESULTS: To test the hypothesis that women have lower tonic ANS support of BP (reduction in intra-arterial BP during acute ganglionic blockade [GB] with intravenous trimethaphan) and less effective baroreflex buffering (BRB) of BP (potentiation of the systolic BP [SBP] response to bolus phenylephrine during versus before GB) than men, 51 healthy adults, 22 premenopausal women (aged 28+/-1 years, mean+/-SE) and 29 men (aged 27+/-1 years), were studied. Women had lower baseline SBP and plasma catecholamine concentrations than men (P<0.05). Tonic ANS support of BP was approximately 50% to 65% lower in the women (P<0.001). The reductions in BP during GB were related to baseline plasma catecholamine concentrations (r=-0.31 to -0.41, P<0.05). Acute BRB of BP was 47% smaller in the women (3.3+/-0.5 versus 6.3+/-0.9, P=0.006) and was related to the SBP responses to phenylephrine before GB (R2=0.71, P