Comparative study of the three neurofilament subunits within pig and human retinal ganglion cells.

PURPOSE Neurofilaments (NF) are neuronal cytoskeletal components and immunostaining against them has been used to visualize retinal ganglion cells (RGC) and their axons. Since the RGC cytoskeleton exhibits differential damage in diseases such as glaucoma, we examined the distribution of light, medium, and heavy NF subunits (NF-L, NF-M, and NF-H respectively) within normal human and porcine retinas, as a function of RGC soma size and eccentricity. METHODS NF subunits were visualized with immunofluorescence techniques using retinal sections and flatmounts from adult human and pig retinas that were incubated with specific antisera against the three NF subunits. Porcine RGCs were retrogradely labeled with fluorogold while human RGCs were identified based on their position within the inner retina and their relatively large somata. RESULTS NF-H and NF-M were distributed widely within all RGC somata and dendrites, whereas NF-L was more restricted to the perinuclear area. In addition, phosphorylated NF-H distribution varied with retinal eccentricity so a subpopulation of large RGCs located in the peripheral retina was intensely labeled with the antiserum recognizing the phosphorylated NF-H. CONCLUSIONS We show that at least one of each of three NF subunits is present in all RGCs in porcine and presumably in human retina, and that NF distribution is very similar in RGCs of both species.