Central hypotensive effects of angiotensin II in the rat

The floor of the fourth cerebral ventricle of urethane-anesthetized rats was exposed through the occipital foramen. Angiotensin II (10-1000 ng), applied onto the surface of the area postrema, induced a rapid lowering of the blood pressure. Pretreatment of the rats with reserpine abolished the hypotensive response to angiotensin II. It is concluded that the local application of angiotensin II induced in the vicinity of the area postrema a release of some biogenic amine, which has an inhibitory effect on the cardiovascular centres.