Nerve growth factor reduces apoptosis of axotomized retinal ganglion cells in the neonatal rat.

It has recently been reported that the degeneration of retinal ganglion cells induced by transection of the optic nerve in the neonatal rat is due to an active process of apoptosis, as opposed to passive necrosis. Here we tested whether the administration of the trophic factor nerve growth factor could prevent the apoptotic death of the axotomized cells. We administered nerve growth factor by two intraocular injections, one immediately after the lesion and the second 12 h later. The retinas were taken at 24 h post-lesion and stained as whole mounts with Cresyl Violet. Pyknotic as well as surviving cells were counted in the retinal ganglion cell layer. In this layer at least 95% of the total cell population is composed by ganglion cells, as revealed by retrogradely labelling these cells with horseradish peroxidase injected in the superior colliculi. We found that intraocular administration of nerve growth factor diminishes the degeneration induced by optic nerve transection in the neonatal rat. After nerve growth factor injection, in fact, the number of pyknotic cells is reduced by 39% compared with controls (lesioned, injected with saline); in addition, nerve growth factor also increases the survival of retinal ganglion cells by 30% at 24 h post-lesion.