Uncrossed retinal projections to the accessory optic nuclei in rabbits and cats

Retinal projections to the accessory optic nuclei of rabbits and cats were demonstrated with standard autoradiographic techniques following intraocular injections of [35S]methionine and [3H]proline. In the pigmented rabbit, albino rabbit, normally pigmented domestic cat and Siamese cat the medial, lateral and dorsal terminal nuclei (MTN, LTN, and DTN, respectively) of the accessory optic system were densely labelled on the side contralateral to the injected eye. An ipsilateral projection, while clearly present in all but the Siamese cat, varied in the number of nuclei involved. In the albino rabbit, the ipsilateral projection ended in the MTN, while in the pigmented rabbit, it ended in the MTN, LTN and DTN, and in the normally pigmented domestic cat it ended in the MTN and LTN. These results indicate that the accessory optic system in rabbits and cats is more extensive than previously reported and that differences exist in the accessory optic system which may be related to genetic differences in normally pigmented and hypopigmented animals.