Angiotensin II contributes to blood pressure maintenance in conscious rats treated with yohimbine.

Yohimbine (1 mg/kg s.c.) produced significant and persistent increases in plasma renin concentration and plasma norepinephrine concentration in conscious rats, but mean arterial pressure (MAP) and heart rate were unchanged. The subsequent i.v. infusion of the angiotensin II receptor antagonist saralasin (100 micrograms/kg per min) caused a significant decrease (-17%) in MAP. We conclude that yohimbine-induced renin release, and the resultant rise in plasma angiotensin II concentration, prevents the decrease in MAP which would result from the blockade of vascular alpha-adrenoceptors by yohimbine.