A small population of retinal ganglion cells projecting to the retina of the other eye. An experimental study in the rat and the rabbit.

We traced the retino-retinal projection with Rhodamine B isothiocyanate (RITC), Rhodamin labelled latex microspheres (RLM), horseradish peroxidase (HRP) and choleratoxin conjugated horseradish peroxidase (BHRP). The number and distribution of ganglion cells projecting to the contralateral eye were recorded. Newborn and young rats have up to about 130 ganglion cells projecting to the other retina; this confirms previous findings. We extended these findings in two ways. First, we describe a similar projection in rabbits consisting of fewer cells; second, we describe the persistence of a small component of this projection into adulthood. In addition we show with RITC and Nuclear Yellow double tracing that some of the retino-retinal ganglion cells have an axon collateral which projects to the superior colliculus. We performed control experiments in order to exclude spillover of tracer which might produce false positive labelling.