Gross persistence of capillary plasma perfusion after middle cerebral artery occlusion in the rat brain

The densities of perfused and existing capillaries were measured in different cortical regions of rat brains after subtemporal occlusion of the middle cerebral artery (MCA). Capillary perfusion patterns (perfused capillaries versus nonperfused capillaries) were verified immediately after MCA occlusion in one group of rats and 1 h later in a second group using fluorescent double staining of capillary morphology and plasma perfusion in identical brain sections. In addition, local cerebral blood flow (CBF) was measured in another group of rats 1 h after MCA occlusion using the autoradiographic iodo-[14C]-antipyrine method. Although cortical CBF was decreased by up to 75% 1 h after MCA occlusion, plasma perfusion was not completely stopped in most capillaries (circulation time of Evans blue, 10 s). Only small patchy perfusion deficits (< 0.1 mm2 of brain section) were detected in the capillaries immediately and 1 h after MCA occlusion in all brains except for one that exhibited a more extensive lack of capillary perfusion. The data show that a drastic reduction of cortical CBF after MCA occlusion is not accompanied by a corresponding amount of nonperfused capillaries.