TIME-DEPENDENT CHANGES IN THE ISCHEMIC FOREBRAIN FOLLOWING THE MICROSPHERE-INDUCED PERMANENT OCCLUSION OF CEREBRAL ARTERIOLES IN RATS

To evaluate the progression of brain edema without modification by the effect of anesthetics, we examined the local and permanent ischemia m odel in unanesthetized rats. The forebrain embolism was induced by int ra-arterial infusion of microspheres of 50-mu m diameter in freely mov ing rats. From 2 to 48 hr following the injection, the water-, Na- and Ca-contents progressively increased while the K content decreased in the microsphere-injected hemisphere. After the 3rd day, the water- and Na-contents gradually decreased and returned to the normal level on t he 14th day. In contrast, the Ca level remained elevated even on the 5 6th day. The animals showed signs of neurological deficits 24 hr after the injection. In histopathological examination, large infarct areas were present in the microsphere-injected hemisphere after 24 to 48 hr. One to two weeks later, the lateral ventricle was expanded. Eight wee ks after the injection, the ventricle remained expanded and newly deve loped infarct areas were observed in a scattered pattern around the fi brotic area. The results show the close correlation between the develo pment of edema and the increase/decrease of Na/K contents from the ons et to the recovery from edema, and their changes are similar to those in human stroke. This model enables us to evaluate not only the acute ischemic insult but also the chronic changes of the forebrain followin g the stroke.