Fig. 8.

Attempts to load dextran-conjugated calcium dyes via the cut optic nerve were unsuccessful in adult rat. Retrograde loading with an equimolar mixture of 10-kDa Alexa Fluor 594-dextran and 10-kDa OGB-1-dextran led to retention of the Alexa dye (A) but not Oregon Green (B). Very weak OGB-1 staining can be seen in some RGC somata, but we could not evoke calcium transients in these cells. Ten-kilodalton fluo-4-dextran (C), 10-kDa fura-dextran (D), and 70-kDa Calcium Green-1-dextran (E) were also not retained by adult rat RGCs even in the presence of probenecid and sulfinpyrazone. Results in adult mice were similar. Scale bars are 100 μm.