[Structure of the pressor reaction to angiotensin]

In anesthetized rats, 1938 blood pressure (BP) responses to i.v. injections of angiotensin II were studied. 6 types and 21 subtypes of responses were distinguished: vasopressor response followed by BP normalizing (type 1; 42%) or by a transitory BP drop (type 2; 7%); BP elevation without its subsequent decrease (type 3; 3%) preliminary sharp increase of BP followed by a "classic" angiotensin pressor effect (type 4; 3%); biphasic response--a depressor response followed by a pressor one (type 5; 27%); depressor response alone (type 6; 18%). Depressor phases were increased by phentolamine and indomethacin, and were inhibited by atropine and spasmolytin. The responses to angiotensin II seem to have a vector character, cholinergic system attenuating this response.