Elevated adrenaline and increased alpha-adrenoceptor-mediated vasoconstriction in essential hypertension.

In patients with essential hypertension, plasma adrenaline, regardless of age, was consistently higher than in normotensive controls; adrenaline correlated with heart rate and the vasodilator response in the forearm circulation produced by postjunctional alpha 1-adrenoceptor blockade with prazosin. This dilator response to prazosin was greater in hypertensive patients. Together, this suggests elevated sympathetic activity and enforced vasoconstriction via postjunctional alpha 1-adrenoceptors in essential hypertension. beta-Adrenoceptor-mediated cardiovascular responses decrease with age and even more with high blood pressure, which contributes to unopposed alpha-adrenoceptor-mediated vasoconstriction. This could explain the transition from an early high cardiac output into a later high peripheral resistance form of hypertension.