Comparative effects of captopril and MK 421 on sympathetic function in spontaneously hypertensive rats

The effects of captopril and MK 421, both orally active angiotensin-converting enzyme inhibitors, on sympathetic function in the pithed spontaneously hypertensive rats were examined. Captopril (100 mg/kg orally) significantly inhibited pressor responses to sympathetic nerve stimulation and norepinephrine whereas MK 421 (10 and 100 mg/kg orally) was without effect. Both drugs abolished the angiotensin I response without affecting that to angiotensin II. Because these doses of MK 421 are antihypertensive in the spontaneously hypertensive rat, it is concluded that inhibition of sympathetic function plays no role in its effect. The role of the sympatholytic action of captopril in its antihypertensive action remains unclear.