Beta‐adrenergic receptors do not offset norepinephrine mediated vasoconstriction in postmenopausal women

Vascular α‐adrenergic receptor sensitivity to norepinephrine (NE) is reduced in young women vs. men, and may be related to increased β‐adrenergic receptor sensitivity in women. Whether this is due to the female sex hormones is unknown. We assessed if forearm vasoconstrictor responses to NE were altered during β‐blockade in young men (n=11), young women (n=12) and postmenopausal women (n=9). Forearm blood flow (FBF, venous occlusion plethysmography) responses to increasing brachial artery doses of NE (2, 4 and 8 ng/100 ml/min) were assessed before and during β‐blockade (propranolol). In young men, % change in FBF from baseline to all doses of NE were similar before and during β‐blockade ( P >0.05 ) . In young women changes in FBF were greater during β‐blockade at 4 (−16 ± 6% vs. −33 ± 4%) and 8 ng/100ml/min (−18 ± 6% vs. −44 ± 3%, P <0.05) of NE. In older women, 2 subjects dilated to all doses of NE, but constricted to NE after propranolol. In the 7 remaining subjects there was no difference in % change in FBF to NE before or during β‐blockade (2 ng/100 ml; −11 ± 4 vs. −14 ± 3%, 4 ng/100 ml; −15 ± 6 vs. −22 ± 5%, 8 ng/100 ml; −22 ± 8 vs. −27 ± 5%, P >0.05). Forearm vasoconstrictor responses to NE are offset by concurrent β‐adrenergic stimulation in young women, but not in young men or most postmenopausal women. These data may explain why blood pressure becomes closely related to sympathetic nerve activity in older women. NIH HL‐083947 (MJJ, NC), AHA 2170087 (ECH), and CTSA RR‐024150.