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 variable degree stenosis of the MCA and the formation of cytotoxic edema in a cat model of acute ischemia. Sodium transport was estimated in synaptosomes isolated from moderately perfused or non-perfused brain tissue. Complete MCA occlusion for 50-75 min produced a major disruption of brain sodium transport, whereas continued preservation of ion homeostasis and the activation of adaptive cell volume regulatory systems was associated with longer duration of moderate severity of ischemia. Preservation of neuronal ion homeostasis might be one of the main mechanisms contributing to the relative tolerance of the brain to moderate reductions in cerebral blood flow.