Flatmounted retinas showing Fluorogold labeled RGCs at 10 days after ON transection and intravitreal injection of Ad.BDNF (a) or vehicle (b). (Bar = 100 μm.) (c) Quantitative analysis of RGC survival in vivo at 10, 16, 21, and 28 days after axotomy and intravitreal administration of 5 μl of Ad.BDNF, recombinant BDNF, Ad.LacZ, or vehicle (n = 3–8 rats per group). At all times examined, significantly greater numbers of RGCs survived in the retinas treated with Ad.BDNF (solid bars) than in the retinas exposed to Ad.LacZ (hatched bars), or vehicle (open bars) (Student’s t test, P < 0.001). RGC densities were similar for the groups of retinas treated with Ad.BDNF (solid bars) or recombinant BDNF (stippled bars) but decreased in all groups at longer times after axotomy.