Cerebral vessels in spontaneously hypertensive rats.

Cerebral arterial vessels of 15- and 200-day-old spontaneously hypertensive rats and normotensive controls were studied concerning the ratio between media thickness and lumen radius. Media/radius ratio among larger vessels was significantly increased already in 15-day-old spontaneously hypertensive rats. Furthermore, the media cross section area and lumen radius was increased in the internal carotid arteries of these animals. The early vascular aberrations could be caused by the slight increase of blood pressure at this age or be due to other genetically determined mechanisms. In 200-day-old hypertensive rats a significantly increased media/radius ratio was seen in arterial vessels with a radius less than 80 microns when compared to local Wistar controls but only in the smallest arterioles (r less than 20 microns) when compared to Kyoto Wistar controls.