Rarefication of the arterioles and capillary network in the brain of rats with different forms of hypertension.

The angioarchitecture of rat brain with deoxycorticosterone acetate (DOCA)-saline and renal forms of experimental hypertension were studied and compared with those of normotensive rats. The number of pial arteries of the third, fourth, and fifth order of branching was lower and their diameter smaller in hypertensive animals as compared with controls. In the medulla oblongata, pons, and mesencephalon the number of arterioles was lower and the total length of capillaries per unit volume was shorter in the experimental group. Rarefication of the capillary network was observed also in rats with spontaneous hypertension. Rarefication was found to begin at the earliest stage of developing hypertension. It was observed as soon as 24 hr after the ligation of the remaining kidney in rats with unilateral nephrectomy. A substantial decrease was recorded in the number of pial arteries with preserved lumens. The hypothesis that the rarefaction of the vascular net in the brain may lead to the formation of zones of ischemia is presented here.