Dendritic morphologies of retinal ganglion cells projecting to the nucleus of the optic tract in the rabbit

Focal injections of Rhodamine‐latex microspheres or Fast Blue were made in the nucleus of the optic tract (NOT) of four rabbits. After survival times of 8–10 days, both dyes were retrogradely transported to medium to large sized ganglion cell somas in the retinas contralateral, but not ipsilateral, to the injected NOT. Most labelled cells were located in or near the visual streak, but a significant percentage were also found in the midperiphery of both the inferior and superior retina. One hundred fifteen labelled cells in four living supervised retinas were impaled under visual control and successfully injected with Lucifer Yellow. The dendritic arborizations of 60 of these were drawn from photographic montages for morphological identification and analysis. Nearly all the injected ganglion cells had large, relatively dense dendritic trees that stratified narrowly in the proximal inner plexiform layer. The dendritic field size and dendritic density of these cells varied with eccentricity, but at all eccentricities their anatomical characteristics closely resembled those of intracellularly stained On directionally selective ganglion cells. In three of the four experiments, a small percentage of ganglion cells were also labelled in the visual streak that had bistratified morphologies resembling those of On‐Off directionally selective ganglion cells.