Projections from the inferior olive to the cerebellar nuclei in the cat demonstrated by retrograde transport of horseradish peroxidase.

The method of intracerebral injections of horseradish peroxidase has been applied to demonstrate a projection from the inferior olivary nucleus to the intracerebellar nuclei in the cat. Cells labeled by the transported enzyme can be observed in different regions of the olive according to the localization of the injection. The caudal half of the medial and dorsal accessory subdivisions, the dorsal cap and nucleus beta project to the fastigial nucleus. In the rostral half of the olive, the accessory subdivisions of that nucleus and the dorsomedial cell column send fibers to the interposed nuclei while the principal olive and the ventrolateral outgrowth are connected with the dentate nucleus. It is likely that these fibers are collaterals of the climbing fibers.