Transplanted rat retinae do not project in a topographic fashion on the host tectum.

We report here that transplanted rat retinae do not project in a topographically organized fashion onto the host tectum. In fact, following the injection of two small non-overlapping regions of the host tectum, one with Fluorogold, the other with Rhodamine conjugated latex microspheres, groups of ganglion cells labelled with either dye are found interspersed throughout the ganglion cell layer of the retinal transplant. The absence of topography in the projections of transplanted retinae offers a new opportunity to examine the mechanisms which lead to topographically ordered projections in normal development.