Brain Edema and Blood–Brain Barrier Opening After Photothrombotic Ischemia in Rat

We have examined the time course of brain edema and the blood–brain barrier opening in rat after basal ganglia ischemia induced by photothrombotic occlusion of the small vessels within the caudate–putamen. Male SD rats were anesthetized, and Rose Bengal dye was intravenously injected. The left caudo-putamen was exposed to cold white light for 5–10 min via a stereotaxically implanted optic fiber. Ischemic brain edema and the blood–brain barrier, as well as the histological changes, were assessed at various times during the following 6 weeks. Local cerebral blood flow was measured 90 min after photothrombosis by quantitative autoradiography. A round infarct with thrombosed parenchymal vessels surrounded by a layer of selective neuronal death was formed within the caudo-putamen. The ischemic lesion turned into a lacune over a period of 6 weeks. A central zone of markedly reduced blood flow and a surrounding oligemic zone were observed 90 min after light exposure. Early blood–brain barrier opening with edema was observed as early as 4 h after photothrombosis, peaked at day 1, and disappeared at 7 days after photothrombosis. In a model of lacunar infarction, we observed an early and transient brain edema and blood–brain opening after onset of ischemia.