MECHANISMS OF BRAIN INJURY ASSOCIATED WITH PARTIAL AND COMPLETE OCCLUSION OF THE MCA IN CAT

High-speed MR diffusion/perfusion imaging was performed to assess vari able degree stenosis of the MCA and the formation of cytotoxic edema i n a cat model of acute ischemia. Sodium transport was estimated in syn aptosomes isolated from moderately perfused or non-perfused brain tiss ue. Complete MCA occlusion for 50-75 min produced a major disruption o f brain sodium transport, whereas continued preservation of ion homeos tasis and the activation of adaptive cell volume regulatory systems wa s associated with longer duration of moderate severity of ischemia. Pr eservation of neuronal ion homeostasis might be one of the main mechan isms contributing to the relative tolerance of the brain to moderate r eductions in cerebral blood flow.