The present study investigated whether rapamycin activated autophagy in retinal ganglion cells (RGC) and evaluated its effect on RGC survival following optic nerve transection (ONT).

The activation of autophagy in RGCs after intravitreal injection of rapamycin was evaluated with the immunohistochemical staining of phospho-S6 ribosomal protein. Rapamycin or 0.1% DMSO was injected intravitreally immediately after ONT. At 1 and 2 weeks after ONT, the RGCs were counted. Rapamycin and autophagy inhibitors, 3-methyladenine or Wortmannin were co-injected intravitreally after ONT and the RGCs were counted 1 week later.

Expression of phospho-S6 ribosomal protein was decreased in RGCs after intravitreal injection of rapamycin. The RGC number was significantly higher in the rapamycin group than in the control group 1 week after ONT. However, the RGC number was not different between the 2 groups 2 weeks after ONT. Repeated intravitreal injection of rapamycin at 1-week intervals showed neuroprotection 2 weeks after ONT. The RGC number was not different between the control group and the co-injection group of rapamycin-autophagy inhibitor.

Activated autophagy by rapamycin was neuroprotective in RGC after ONT.