The sympathetic nervous system and converting enzyme inhibition.

Angiotensin II appears to have important actions in modulating sympathetic nerve activity; conversely, sympathetic stimulation alters renin release. Drugs that inhibit angiotensin II formation would be expected then not only to offset the direct vasoconstricting and aldosterone releasing actions of this peptide but also to reduce sympathetic nerve activity. Hypertension and cardiac failure are two major conditions in which converting enzyme inhibitors have found important therapeutic roles; both are considered to be associated with increased activity of the renin-angiotensin-aldosterone and sympathetic nervous systems. However, in spite of considerable experimental evidence for a sympatholytic action of converting enzyme inhibitors, direct proof has been difficult to obtain in humans. In part, this results from the lack of any satisfactory way of assessing sympathetic activity in the clinical situation. Nevertheless, our failure to understand the pathophysiology of disease and the precise mechanism of action of drugs has not precluded exploiting the salutatory effects of inhibition of converting enzyme.