Retinal ganglion cell topography in teleosts: a comparison between Nissl-stained material and retrograde labelling from the optic nerve

The retinal topography of cells within the ganglion cell layer of three teleost species is examined in Nissl-stained material in which all neuronal elements containing Nissl substance in the cytoplasm are counted. A topographic comparison is made with retrogradely labelled ganglion cells to differentiate the proportion of nonganglion cells not possessing an axon joining the optic nerve. In the three species studied 92%, 80%, and 66% were found to be the maximum proportion of true ganglion cells in the area centralis, horizontal streak, and periphery, respectively. The proportion of nonganglion cells in the total population of cells counted was 24%. The major contribution to this discrepancy is from peripheral nonspecialized regions of the retina. There is little difference in both topography and peak densities of retinal ganglion cells between the two techniques. The soma areas of both populations are analysed, with the homogeneous nonganglion cell population possessing cells between 5 and 15 micron2 and the heterogeneous ganglion cell soma between 5 and 68 micron2, increasing in size with eccentricity.