Survival of neurons after partial crush injury of the optic nerve in Lew, SPD, and F344 rats. The optic nerves of adult Lew, SPD, and F344 rats were subjected to a partial crush injury 1–2 mm from the eye, using calibrated cross-action forceps. Two weeks later, the optic nerves were exposed for the second time, and the fluorescent dye 4-Di-10-Asp was applied distally to the injury site. Five days after dye application, the retinas were detached from the eyes and prepared for fluorescence microscopy as described in Figure 1. The amount of endogenous neuroprotection was significantly greater in F344 and SPD rats (p < 0.01 andp < 0.001, respectively), known to be resistant to EAE induction. **p < 0.01; ***p < 0.001; Student's t test.