Effect of aging on carotid baroreflex control of blood pressure and leg vascular conductance in women

Recent work suggests that beta-adrenergic vasodilation offsets alpha-adrenergic vasoconstriction in young women, but this effect is lost after menopause. Given these age-related vascular changes, we tested the hypothesis that older women would exhibit a greater change in vascular conductance following baroreflex perturbation compared with young women. In 10 young (21 +/- 1 yr) and 10 older (62 +/- 2 yr) women, mean arterial pressure (MAP; Finometer), heart rate (HR), cardiac output (CO; Modelflow), total vascular conductance (TVC), and leg vascular conductance (LVC, duplex-Doppler ultrasound) were continuously measured in response to 5-s pulses of neck suction (NS; -60 Torr) and neck pressure (NP; +40 Torr) to simulate carotid hypertension and hypotension, respectively. Following NS, decreases in MAP were similar between groups; however, MAP peak response latency was slower in older women (P < 0.05). Moreover, at the time of peak MAP, increases in LVC (young, -11.5 +/- 3.9% LVC vs. older, +19.1 +/- 7.0% LVC; P < 0.05) and TVC were greater in older women, whereas young women exhibited larger decreases in HR and CO (young, -10 +/- 3% CO vs. older, +0.8 +/- 2% CO; P < 0.05). Following NP, increases in MAP were blunted (young, +14 +/- 1 mmHg vs. older, +8 +/- 1 mmHg; P < 0.05) in older women, whereas MAP response latencies were similar. Interestingly, decreases in LVC and TVC were similar between groups, but HR and CO (young, +7.0 +/- 2% CO vs. older, -4.0 +/- 2% CO; P < 0.05) responses were attenuated in older women. These findings suggest that older women have greater reliance on vascular conductance to modulate MAP via carotid baroreflex, whereas young women rely more on cardiac responsiveness. Furthermore, older women demonstrate a blunted ability to increase MAP to hypotensive stimuli.