Experimental cerebral atherosclerosis in the rabbit. Scanning electron microscopic study of the initial lesion site.

The development and initial lesion sites of cerebral atherosclerosis were studied in hypertensive rabbits fed 0.5 g/day cholesterol in their diet. The earliest lesions developed at remarkably localized areas of the basilar artery-posterior cerebral artery Y-bifurcation (area A) and vertebral arteries-basilar artery confluence (area B). These findings were obtained from a thorough scanning electron microscopic survey of the dorsal surface of the cerebral artery segment covering from the vertebral arteries to the posterior cerebral arteries. By light microscopy intimal lesions were mainly composed of accumulations of foam cells and smooth muscle cells. Electron microscopically foam cells accumulated in the intima resembled those of a monocyte-macrophage lineage. Early lesions involving only a few endothelial cells with adherent leukocytes occurred at the dividing and confluent portions of the endothelial arrays formed in areas A and B, respectively. The results indicate that hypertension coupled with hypercholesterolemia induces atherosclerosis in particular vulnerable regions of the cerebral arteries.