Critical period for degradation of adult rat retinal ganglion cells and their regeneration capability after axotomy.

The optic nerve (ON) in adult rats was transected intraorbitally followed by retrograde labelling of retinal ganglion cells (RGCs) with fluorescence dye (DiI). A two phase reduction of axotomized RGCs was represented in the retina until 15 days after ON transection. The critical period of RGC loss is around 7 days after axotomy. In this period, the capability of neurite regeneration from RGCs in culture was strongly intensified by ON transection. These findings indicate that the 7th day after axotomy is important for both RGC survival and regeneration.