Time courses of progress to the chronic stage of middle cerebral artery occlusion models in rats

Several kinds of middle cerebral artery occlusion model in rats have been developed. Variable ischemic inductions are attributed to the different contributing factors in ischemic damage formation. In the present study, we examined the differences in ischemic induction attributed to chronic stage. Male Sprague-Dawley rats were subjected to two kinds of middle cerebral artery occlusion model, a thermocoagulation and a photothrombosis model. We compared the changes in body weight, neurological outcome, size of ischemic damage, brain edema and atrophy formation, and histological data for 84 days between a thermocoagulation and a photothrombosis model in rats. Although the time courses of infarction formation were no different, there were differences in the time courses of brain edema, atrophy formation, and neuronal deficits between the models. Microinfarction formation was observed as a characteristic of the photothrombosis model. The present study demonstrated that differences in ischemic induction did not affect maturation of infarct size, brain atrophy, or neuronal deficits 84 days after ischemia. However, the progress of maturation was different between the models. The possibility that reperfusion contributed to the time course of brain edema and atrophy was considered, and it was suggested that brain edema formation influenced neurological outcome.