Figure 14.

Effects of brachial artery administration of norepinephrine (noradrenaline, NA) on forearm vascular conductance before and after local administration of the non-selective β-blocker propranolol (BB). In young women (panel A) increasing doses of NA did not evoke marked vasoconstriction at rest. However, marked vasoconstriction is seen after administration of propranolol. In postmenopausal women propranolol had no effect and the constriction caused by administration of NA caused more marked vasoconstriction. In men, β-blockade has little effect on these responses (not shown). The responses indicate that concurrent β-adrenergic vasodilation limits α-adrenergic vasoconstriction in young women. This sex difference might explain many of the findings highlighted in Figures 7, 8, and 9. Data from (43).