Evidence for prejunctional inhibition of norepinephrine release by captopril in spontaneously hypertensive rats

Pretreatment of spontaneously hypertensive rats (SHR) with the converting enzyme inhibitor captoril (10 or 100 mg/kg p.o.) had no effect on pressor responses to angiotensin II or norepinephrine whereas the response to angiotensin I was markedly inhibited. In contrast, pressor responses to symphathetic stimulation in pitched SHR were inhibited by captoril whereas the positive chronotropic responses to stimulation were unaltered. These results suggest that captoril causes a prejunctional inhibition of norepinephrine release to sympathetic nerve stimulation which is selective for the vasculature. This is probably due to inhibition of angiotensin II formation in the vasculature.