The effect of yohimbine on sympathetic responsiveness in essential hypertension

Summary We have studied the sympathetic response to blockade of presynaptic ₂-adrenoceptors in essential hypertension by measuring plasma concentrations of noradrenaline after a single oral dose of yohimbine, an ₂-adrenoceptor antagonist.Mean baseline plasma noradrenaline and adrenaline concentrations were similar in the hypertensive and normotensive groups. Yohimbine (0.2 mg×kg^–1 orally) caused a lesser increase in the plasma concentrations of noradrenaline in hypertensive patients (+67%) than in normotensive subjects (+178%) and a pressor response in hypertensive (but not in normotensive) patients.These results are consistent with an alteration in the balance of -adrenoceptors (for example presynaptic ₂-adrenoceptor desensitization and post-synaptic ₁-adrenoceptor hyper-responsiveness) which would help to develop and/or maintain arterial hypertension.