FIGURE 6.

Axon injury and microglial activation in the optic nerve. Confocal images of optic nerve sections from mice 3 days after impact TBI, taken from the region just beyond the extraocular muscle cone, immunostained with SMI-32 to detect injured axons and for IBA1 to reveal microglia. (A) Large SMI-32+ axon bulbs (magenta) and intensely stained microglia (green), indicative of injury to the nerve, are visible in the image from an impact-vehicle mouse. Note that, by contrast, in sham mice, axon bulb pathology is absent (and thus not shown here) and microglia are lightly labeled for IBA1 (see Figure 7A). (B) Microglia with more rounded shapes are present in impact mice treated with 10 mg/kg raloxifene, one of which appears to be engulfing an axon bulb. (C) Numerous microglia are seen clustered together, amidst a field of small SMI-32+ profiles that resemble debris from degenerating axons. (D–F) Higher-magnification views of the regions shown boxed in (C). The small arrow in (D) marks an especially large axon bulb. The larger arrow in (E) indicates a rounded microglial cell that appears to be engulfing an axon bulb. Scale bar in (A) applies to (A–C), and scale bar in (D) applies to (D–F).