An autoradiographic study of the subcortical projections of the rabbit striate cortex in the adult and during postnatal development.

The subcortical projections of the rabbit striate cortex were studied by autoradiography. Small injections of 3H-leucine were placed into the striate cortex of 15 rabbit pups aged between one day and one month and six adult rabbits (strain Chbb:Ch). Terminal fields of projection occurred only ipsilateral to the injection, and these were found in the caudate nucleus (CN), the claustrum (Cla), the thalamic reticular nucleus (TRN), the dorsal (LGNd) and the ventral (LGNv) lateral geniculate nuclei, the pulvinar (Pul), the ventrolateral (Vl) the posterior (Po) thalamic nuclei, the anterior (APN) and posterior (PPN) pretectal nuclei, the nucleus of the optic tract (NOT), the superior colliculus (SC) and the basal pontine nuclei (PN). Cla was innervated via the superficial corticocortical and CN via the corticocaudate pathways. The remaining projections were innervated via the subcortical pathway which comprised three bundles: The deep bundle (to TRN, LGNd, Pul and Po), the superficial bundle (to LGNv, APN, PPN, NOT, and SC), and the peduncular bundle (to PN). The projection to SC showed remarkable changes of its terminal pattern during the first and second postnatal weeks. These changes were characterized by a strong reduction of the horizontal extension of the terminal labelling and an increasing concentration on the stratum griseum superficiale. Similar changes were not observed in the other projections.