Potassium-Induced Cortical Spreading Depressions during Focal Cerebral Ischemia in Rats: Contribution to Lesion Growth Assessed by Diffusion-Weighted NMR and Biochemical Imaging

In focal ischemia of rats, the volume of ischemic lesion correlates with the number of peri-infarct depolarizations. To test the hypothesis that depolarizations accelerate infarct growth, we combined focal ischemia with externally evoked spreading depression (SD) waves. Ischemic brain infarcts were produced in halothane-anaesthetized rats by intraluminal thread occlusion of the middle cerebral artery (MCA). In one group of animals, repeated SDs were evoked at 15-min intervals by microinjections of potassium acetate into the frontal cortex. In another group, the spread of the potassium-evoked depolarizations was prevented by application of the N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801). The volume of ischemic lesion was monitored for 2 h by diffusion-weighted imaging (DWI) and correlated with electrophysiological recordings and biochemical imaging techniques. In untreated rats, each microinjection produced an SD wave and a stepwise rise of the volume and signal intensity of the DW...