A Role for Brain Angiotensin II in Experimental Pregnancy-Induced Hypertension in Laboratory Rats

The Sprague-Dawley laboratory rat served as an experimental model for pregnancy-induced hypertension. Generation of systemic hypertension depended upon a surgical reduction of blood pressure by 30–35% to the uteroplacental unit. Blood pressures during the final trimester of rat pregnancy typically rose from a normal of 125/80 mm Hg to 160/100 mm Hg within 4 days of surgery; they fell to normal by 5 days post partum. A 7.5-fold rise in proteinuria accompanied development of the hypertension. Hypertension was reversed acutely by injection of the angiotensin II antagonist, saralasin, into the brain ventricular system; intravenous saralasin injection elicited no observable response. Intraventricular injection of the alpha-2 adrenergic agonist, clonidine, did not lower blood pressure in experimental rats. We conclude that the experimental pre-eclampsia observed in these rats depends upon a central nervous system angiotensin II mechanism and not upon enhanced activation of the sympathetic nervous system.