BRAIN CAPILLARY DENSITY AND CEREBRAL BLOOD-FLOW AFTER OCCLUSION OF THE MIDDLE CEREBRAL-ARTERY IN NORMOTENSIVE WISTAR-KYOTO RATS AND SPONTANEOUSLY HYPERTENSIVE RATS

Objective: In order to elucidate why spontaneously hypertensive rats ( SHR) develop larger brain infarcts distal to an arterial occlusion tha n normotensive Wistar-Kyoto (WKY) rats, we determined the surface and volume densities of cerebral capillaries, and the regional cerebral bl ood flow distal to an arterial occlusion in SHR and WKY rats. Design: Occlusion of the middle cerebral artery was chosen because the middle cerebral artery territory is most commonly affected by cerebral infarc ts in man. Methods: Surface and volume densities of capillaries in the neocortex of the middle cerebral artery territory were measured by st ereological techniques on histological sections. Fifteen minutes after ligation of the right middle cerebral artery, regional cerebral blood flow was measured autoradiographically by the [C-14]-iodoantipyrine m ethod. Results: The capillary density of the neocortex did not differ between the SHR and WKY rats. The blood flow was significantly lower w ithin the middle cerebral artery territory in the SHR than in the WKY rats. Conclusions: The reduced blood flow distal to the occlusion in S HR is probably a consequence of structural adaptation of arterial resi stance vessels, rather than being caused by reduced capillary density.