Sympathetic nervous activity and noradrenaline reactivity during angiotensin converting enzyme inhibition

The effect of the angiotensin converting enzyme inhibitor ramipril on catecholamine disposition and noradrenaline reactivity was studied in normotensive volunteers. In the first study 5 mg of ramipril or placebo was given 3 times at 12-hour intervals in a randomized, double-blind, cross-over manner (n = 10). In the second study, ramipril 10 mg daily was given for 2 weeks (n = 6). Noradrenaline reactivity increased significantly (p less than 0.05) both in short- and long-term application, while blood pressure decreased (p less than 0.01). Sulfoconjugated plasma noradrenaline decreased significantly (p less than 0.05) possibly indicating a decrease in sympathetic tone. These findings suggest that a decrease in sympathetic tone could contribute to the blood pressure-lowering effect of ramipril, whereas the increase in noradrenaline reactivity is probably a consequence of the primary change in sympathetic activity.