Fig. 3

Histological analysis of SD-related tissue injury. a Representative background subtracted IOS images to the left show the surface of the cortex covered by the propagating SD (bright region). White arrowheads are pointing at the position of the site of SD elicitation with KCl or ES. In the middle, representative light microscopic images of brain slices stained with TTC after the passage of SDs (4–4 SDs were elicited in each slice with KCl or ES; a single SD occurred in response to HM or OGD) show macroscopic injury. Representative photomicrographs of hematoxylin–eosin-stained sections to the right demonstrate neuronal injury. Black arrowheads indicate injured neurons; white arrowheads show viable cells with intact nuclei in the somatosensory cortex. b The number of TTC-stained cellular compartments (i.e. particles). c Correlation between the number of particles and the cortical area bearing an SD as in Fig. 2b. Data are given as mean ± stdev. Sample size (i.e. number of slices analyzed) is indicated in each bar. ES bipolar electric field stimulation, KCl microinjection of 1 M KCl solution, HM hypo-osmotic medium, OGD oxygen–glucose deprivation. Statistical analysis relied on one-way analysis of variance (ANOVA) followed by a Holm-Sidak post hoc test (b), or one-tailed Pearson correlation analysis (c). The level of significance is given as p < 0.05* and p < 0.01** vs. KCl; p < 0.01 ^## and p < 0.001 ^### vs. ES; p < 0.05 ^$ vs. HM