Changes of the cerebral microvascular structure and endothelium during the course of permanent ischemia

In cerebral ischemia, ultrastructural changes of the microvessels were investigated in relation to the further development of microcirculatory disturbances. Experimental ischemia was induced by occlusion of the unilateral common carotid artery (CCA) in mongolian gerbils. The animals were sacrificed at set times ranging from 6 to 96 hours after the occlusion. After 6 hours of ischemia, swelling of perivascular astrocytic processes was seen, although there were no obvious changes in the endothelium. After 12 hours, perivascular glial swelling became more prominent and narrowing of the microvascular lumen was observed. After 24 or 48 hours, an irregular luminal surface with endothelial projections was noted. These changes may have had some influence on the brain microcirculation. At 96 hours of ischemia, the cytoplasm of the endothelium appeared granular and thrombus formation was occasionally observed on the exposed basement membrane of those microvessels whose endothelium had been exfoliated. Thus, in the permanent ischemia of the present study, exfoliation of endothelium was thought to have caused the thrombus formation, promoting further microcirculatory disturbance and consequent progress of the brain damage.