a Upper panel: Representative images obtained from the cerebral cortex of 4 h pMCAO animals illustrating that FITC-albumin (FITC) extravasations are found at the border zone of downregulated MAP2 expression, which represent penumbral areas. Collagen IV was used to identify cerebral vessels while nuclei are visualized with DAPI. Lower panel: In 4 h pMCAO animals, FITC-albumin extravasations are found in areas of neuronal HSP70 up-regulation, again representing areas of the ischemic penumbra. Of note, FITC-albumin extravasations are not restricted to penumbral areas, but are also found in striatal areas of the presumed ischemic core, which are lacking a selective HSP70 up-regulation in neurons. NeuN is used to identify neurons, while nuclei are visualized with DAPI. Scale bars: 50 μm. b Analysis of the mean fluorescence intensity of extravasated FITC-albumin (left) and the extravascular FITC-albumin spreading (right) in regions with neuronal HSP70 expression (penumbra) and lacking HSP70 expression (core). Data are obtained from different fields of view (FOV) at lower magnification (20×) from the ischemia-affected cortex. Direct comparison between core and penumbra failed to provide statistically significant differences (left: p = 0.345; right: p = 0.26; each n = 4, ANOVA followed by Bonferroni’s multiple comparison test). Data are given as means. Error bars indicate SD.