An autoradiographic study of the retinotectal projection in the golden hamster

Intraocular injections of tritiated leucine and proline were used to examine the retinotectal projection of the golden hamster. In the contralateral superior colliculus intense and complete label was seen in the stratum zonale, stratum griseum superficiale and the upper portion of the stratum opticum, with relatively less dense label in the lower part of the optic layer. On the ipsilateral side no label was found in the most rostral portion of the tectum. This area comprised about 10% of the rostro-caudal extent of the colliculus, and most likely, it receives a crossed input from the temporal retina (as demonstrated in the cat by Harting and Guillery, '76). Very sparse label was observed in an anterior segment of the ipsilateral colliculus. In coronal sections it appeared as discrete clumps or patches which were confined to the stratum opticum. Within this layer there was a tendency for the clumps to be located more dorsally with increasing laterality. There was considerable variability between and within animals in the size of the clumps as well as the distance between clumps. Reconstruction of coronal sections showed that the ipsilateral label forms discontinuous ribbons which extend up to 180 microns in the rostro-caudal dimension. No label was seen on the ipsilateral side in the remaining tectum (caudal 60%).