To investigate the retrograde degeneration of primate retinal neurons, the left optic nerves of 3 Formosan rock monkeys were transected intraorbitally. The pattern of organization of protein gene product 9.5 (PGP 9.5), a specific neuronal marker, and synaptosomal associated protein 25 kDa (SNAP-25), were examined 1 mo after axotomy. A severe loss of retinal ganglion cells and their axons was observed, while photoreceptors became reactive in the lesioned retina as detected by PGP 9.5 immunoreactivity. A significant decrease of PGP 9.5 and SNAP-25 immunoreactivity in the plexiform and nerve fiber layers was also detected in the retina ipsilateral to the axotomized retina. The sublayers were mixed and indistinguishable in some areas of the lesioned retina, indicating that degeneration occurred not only in the retinal ganglion cells but also in other populations; further, the alteration was more severe in the monkey retina as compared with results from our previous studies performed in the rodent optic system. Our findings also show that PGP 9.5 and SNAP-25 are good markers for investigating the effects of neuronal injury and the mechanisms that underlie the processes of neuronal degeneration.
PGP 9.5, SNAP-25, Retina, Degeneration, Monkey
