DEMONSTRATION OF RETINAL AFFERENTS IN THE RCS RAT, WITH REFERENCE TO THE RETINOHYPOTHALAMIC PROJECTION AND SUPRACHIASMATIC NUCLEUS

In the Royal College of Surgeons (RCS) rat, characterized by inherited retinal dystrophy, retinal projections to the brain were studied usin g anterograde neuronal transport of cholera toxin B subunit upon injec tion into one eye. The respective immunoreactivity was found predomina ntly contralateral to the injection site in the lateral geniculate nuc leus, superior colliculus, nucleus of the optic tract, medial terminal nucleus of the accessory optic tract, and bilateral hypothalamic supr achiasmatic nuclei. Although terminal density was somewhat reduced in dystrophic rats, the projection patterns in these animals appeared sim ilar to those seen in their congenic controls and were comparable to t he visual pathways described for the rat previously. In dystrophic rat s, the number of cell bodies exhibiting immunoreactivity to vasoactive intestinal polypeptide, viz. a population of suprachiasmatic neurons receiving major retinohypothalamic input, was reduced by one-third, an d some differences were observed in the termination pattern of the gen iculohypothalamic tract, as revealed by immunoreactivity to neuropepti de Y in the suprachiasmatic nucleus.