Retrograde fluorescent microsphere tracing of retinal and central afferents to the nucleus of the optic tract in pigmented and albino rats

The pretectal nucleus of the optic tract is involved in optokinetic nystagmus. Albino animals suffer from inverse optokinetic nystagmus, possibly due to a smaller number of ipsilateral projections. Animals with laterally placed eyes have an asymmetric nystagmus, attributed to a presumed lack of binocular cortical input to the nucleus of the optic tract. Moreover, a direct input from the ipsilateral retina is controversial. We investigated the retinal and central afferents to the nucleus of the optic tract in the rat by retrograde tracing using fluorescent latex microspheres. Ipsilaterally projecting retinal ganglion cells were observed in pigmented and also in albino rats. Projections from the visual cortex and primary visual nuclei were demonstrated.