SOMA AND AXON DIAMETER DISTRIBUTIONS AND CENTRAL PROJECTIONS OF FERRET RETINAL GANGLION-CELLS

Using a combination of retrograde horseradish peroxidase (HRP) labelli ng, silver staining, and electron microscopy, we have assessed the rel ationship between retinal ganglion cell soma size and axon diameter in the adult ferret (Mustela putorius furo). Retinal ganglion cells were labelled following injections of HRP into the lateral geniculate nucl eus (LGN), superior colliculus (SC), or LGN+SC. The soma size distribu tions following LGN, SC, or LGN+SC injections were all unimodal showin g considerable overlap between different cell classes. This was confir med for alpha cells, identified on the basis of dendritic filling or f rom neurofibrillar-stained retinae. Analysis of the soma size and axon diameters of a population of heavily labelled retinal ganglion cells showed a significant correlation between the two. However, the overall distribution of intraretinal axon diameter was bimodal with an extend ed tail. Analysis of the ganglion cell distributions in the adult ferr et indicates that beta cells comprise about 50.5-55%, gamma 42.5-47%, and alpha 2.5% of the ganglion cell population. This implies that the proportion of gamma, beta, alpha cells in both cat and ferret retina i s highly conserved despite differences in visual specialization in the two species.