Antihypertensive drugs and the sympathetic nervous system

The sympathetic nervous system (SNS) plays an important role in the regulat ion of blood pressure homeostasis and cardiac function. Furthermore, the in creased SNS activity is a predictor of mortality in patients with hypertens ion, coronary artery disease and congestive heart failure. Experimental dat a and a few clinical trials suggest that there are important interactions b etween the main presser systems, i.e. the SNS, the renin-angiotensin system and the vascular endothelium with the strongest vasoconstrictor, endotheli n. The main methods for the assessment of SNS activity are described. Cardi ovascular drugs of different classes interfere differently with the SNS and the other pressor systems. Pure vasodilators including nitrates, alpha -bl ockers and dihydropyridine (DHP)-calcium channel blockers increase SNS acti vity. Finally, central sympatholytics and possibly phenylalkylamine-type ca lcium channel blockers reduce SNS activity. The effects of angiotensin-II r eceptor antagonists on SNS activity in humans is not clear; experimental da ta are discussed in this review. There are important interactions between t he presser systems under experimental conditions. Recent studies in humans suggest that an activation of the SNS with pure vasodilators in parallel in creases plasma endothelin. It can be assumed that, in cardiovascular diseas es with already enhanced SNS activity, drugs which do not increase SNS acti vity or even lower it are preferable. Whether this reflects in lower mortal ity needs to be investigated in intervention trials.