The sympathetic nervous system in the pathogenesis of hypertension.

There are now numerous studies demonstrating that essential hypertension is accompanied by sympathetic activation. Using drugs which block cardiac sympathetic effects, it could be shown that a noticeable fraction of subjects with borderline hypertension had an increased sympathetic drive. A meta-analysis of studies on plasma noradrenaline levels as an indirect marker of sympathetic tone reported that noradrenaline concentrations were significantly elevated in patients with essential hypertension as compared with normotensive control subjects. In addition, it could be shown that the rate of noradrenaline spillover from sympathetic nerve terminals was sometimes increased in essential hypertension, particularly in young hypertensive subjects. Additional data have emerged by direct measurement of sympathetic nerve traffic to skeletal muscle circulation using a microelectrode technique. Most studies using this method have demonstrated increased sympathetic nerve activity in patients with essential hypertension. In contrast, patients with secondary hypertension did not differ from normotensive subjects. Taken together, the data available at present show that sympathetic activation is a specific feature of essential hypertension and that it may play a pathogenetic role in this disease.