Carotid and Cerebral Arteriosclerosis in the Rat

Male and female breeder rats spontaneously develop arteriosclerosis. This occurs first in the aorta and coronary arteries and subsequently in the carotid and intracranial arteries. The carotid arteries show mesenchymal cell proliferation in the media followed by subintimal swelling and mucoid deposition, elastosis, cartilaginous metaplasia and eventual bone formation. Lipid deposition occurs infrequently, and then only in advanced lesions in the media. Severe lesions are much more frequent in the female breeder and the tendency towards cartilaginous metaplasia and bone formation is peculiar to the carotid arteries. The cerebral arteries show little arteriosclerotic involvement except for aneurysm-like outpouchings of the internal elastic membrane associated with mucopolysaccha-ride accumulation about the sites of elastic tissue disruption. Despite severe fulminating arteriosclerosis in the carotid arteries, the cerebral arteries and the brain tissue itself show little or no significant evidence of degenerative change. These results are interpreted to mean that the cerebral arteries of the breeder rat follow a different physiological and morphological pattern of response than the rest of the arterial system.