Differential increases in rat retinal ganglion cell size with various methods of optic nerve lesion

Optic nerve injury is a well established paradigm for studying a variety of neuronal responses, although the actual method of nerve severance is rarely taken into account. This study assessed changes to ganglion cell size in three different methods of optic nerve lesions. Adult rats underwent either one of two types of mechanical nerve crush, or an axotomy. Ganglion cells were visualised by retrograde labelling from the optic nerve with 4Di-10ASP, and soma size measured. Two weeks after lesion, mean soma size was increased in all groups. However, at 4 weeks, the crush groups continued to show an increase (60.5% larger than normal), while the mean cell size in the axotomy group was almost at normal levels (0.2% smaller than normal). This study supports the hypothesis that axotomy, and not simple crush, deprives ganglion cells of substances beneficial to cell survival.