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Fig. 2
Microglial response to telencephalic injury is rapid and extensive. (A,D) Within 24 h post injury, 4C4-immunoreactive microglia appear in large numbers in the ipsilesional telencephalic hemisphere following both QA- (B) and vehicle-induced (D) lesions. Substantial numbers of microglia are also seen in the contralesional hemisphere (A, C) compared with the intact brain. (E–H) Microglial numbers peak at 48 h post injury in both the ipsilesional (F,H) and contralesional (E,G) hemispheres, with more widespread microglial presence in QA- (E-F, Y) relative to vehicle-induced (G,H,Y) injury. (I–T) The microglial response persists at lower levels on days 4 and 7 after injury, and returns toward baseline levels by 14 days. (U–U23) Microglia in the parenchyma proliferate as an early response to injury as shown by incorporation of EdU 24 h post-lesion. (Y) Quantification of the microglial reaction after QA or vehicle lesioning. The percent area of 4C4 immunoreactivity is more extensive following QA-induced than vehicle-induced injury in the ipsilesional hemisphere at all timepoints measured as well as in the contralesional hemispheres at 2, 4, and 14 dpl. ANOVA results indicated significant main effects for lesion type (F(1, 66) = 24.586, P < 0.0001), dpl (F(3, 66) = 37.330, P < 0.0001), and hemisphere (F(1, 66) = 46.988, P < 0.0001), with significant interaction effects for type of lesion x dpl (F(3, 66) = 3.577, P < 0.018), type of lesion x hemisphere (F(1, 66) = 6.051, P < 0.017), and dpl x hemisphere (F(3, 66) = 9.491, P < 0.0001). Significant post hoc analyses (Tukey HSD) were followed by pairwise comparisons with Bonferroni correction; significant results are indicated on the graph. Scale bar = 100 µm.