The retinal projections to the ventral and dorsal divisions of the medial terminal nucleus and mesencephalic reticular formation in the Japanese monkey (Macaca fuscata): a reinvestigation with cholera toxin B subunit as an anterograde tracer.

After a monocular injection of the cholera toxin B subunit (CTB) into the vitreous chamber of the eye, retinal projections to the medial terminal nucleus (MTN) of the accessory optic system (AOS) were studied in the Japanese monkey. The anterogradely transported tracer was visualized with the peroxidase antibody technique by using an anti-cholera toxin antibody. One small accumulation of the CTB-immunopositive retinofugal terminals was located in a small area just medial to the medial edge of the cerebral peduncle and anterior to the attachment of the oculomotor nerve, suggesting the existence of a ventral division of the MTN of the AOS. Caudally, one very small bundle of the retinofugal fibers extending dorsally from this accumulation was seen running along the medial edge of the cerebral peduncle and substantia nigra to the small region corresponding to the dorsal division of the MTN. A few small bundles of CTB-immunopositive retinal fibers were observed to leave the superior fasciculus of the AOS at various points. These fibers coursed medially through the cerebral peduncle and substantia nigra to reach some restricted areas of the mesencephalic reticular formation between the medial lemniscus and the substantia nigra.