Figure 3.

SDF promotes the survival of cultured RGCs without promoting the translocation of TrkB to the cell surface. A, RGC survival is enhanced by 10 μm forskolin (p = 0.002) to the same degree as by 100 ng/ml SDF-1 (p = 0.001). The average percentages of surviving RGCs at 72 hr compared with 24 hr are shown for three independent experiments. p values were calculated by comparing each population with the untreated one using a two-tailed test with different variances. B, SDF-1-promoted survival is not affected by the src family inhibitor PP1, whereas BDNF survival is completely blocked. C–E, Forskolin but not SDF-1 induces the translocation of TrkB to the surface of RGCs. After 24 hr, cultures were left untreated (C1, C2) or treated for 30 min with 10 μm forskolin (D1,D2) or 100 ng/ml SDF-1 (E1,E2). All cultures were then stained live with anti-rabbit TrkB antibody. RGCs are visualized in green with anti-islet-1 (C1–E1), and surface TrkB is visualized in the same fields in red (C2–E2) (20×). Although both forskolin and SDF-1 promote the survival of RGCs, forskolin induces the translocation of TrkB to the surface of retinal cells, whereas SDF-1 does not.