Delayed but not early tPA treatment exacerbates ischemic brain injury. (A) Mice were subjected to 40-minute occlusion and administered vehicle or tPA at 40 minutes postinjury (n = 8 per group). (B) Mice subjected to 40-minute occlusion were administered vehicle or tPA in the presence or absence of IFNβ at 3 hours postreperfusion (n = 8 per group). 24 hours after disease onset, ischemic brains were harvested and subjected to TTC staining. Two representative TTC-stained brain samples of each group are shown. The infarct volume of ischemic brains was also measured. ***P < .001 by 1-way analysis of variance (ANOVA). Not significant (N.S.) by unpaired Student t test (A) or 1-way ANOVA (B).