Histochemical and morphometric investigation of the pathogenesis of acute brain infarction in primates.

The right medial cerebral artery of 25 primates (Macaca radiata) was occluded transorbitally with an atraumatic clip. The time courses of infarct volume and capillary morphometric changes in the ischemic lenticular nucleus, caudate nucleus and insular cortex were then determined. Volume changes of ischemic foci were studied morphometrically using an enzyme histotopochemical acid phosphatase stain. During the first 4 hours extension (or spread) of the ischemic area was small and constant. Over the next hours, the ischemic focus increased in volume, becoming maximal in the lenticular nucleus in 24 hours and in the caudate nucleus in 48 hours. In the lenticular nucleus, edema developed 4 hours after onset of ischemia and was characterized by a decrease in capillary diameter and an increase in mean intercapillary distance. In the caudate nucleus and insular cortex, in the first hours after clipping the medial cerebral artery, capillary diameter and volume increased and intercapillary distance decreased. The data demonstrate that the therapeutic window of brain infarct treatment is during the first 4-6 hours after occlusion of the medial cerebral artery.