Zonal organization of olivocerebellar projections to the uvula in rabbits.

Olivocerebellar projections to the uvula were studied by means of retrograde axonal transport of horseradish peroxidase (HRP) in pigmented rabbits. The distribution pattern of labeled cells in the inferior olive was compared among cases following large- and microinjections of HRP into the uvula. Findings indicate topographically organized projections to longitudinally oriented zones. There are at least 6 zones in the rabbit's uvula. The caudal part of the nucleus beta projects contralaterally to a most medially located zone (caudal beta zone). The rostral part of the nucleus beta projects to a little more laterally located zone (rostral beta zone) at a distance of about 1 mm from the midline of the uvula. The caudolateral part of the MAO projects to a zone (caudolateral MAO zone) located laterally to the rostral beta zone. The dorsomedial cell column projects to a zone (dorsomedial cell column zone) located in the intermediate part of the uvula at about 2 mm from the midline. The rostrolateral part of the MAO projects to the most lateral zone (rostrolateral MAO zone) of the uvula. Finally, the ventral lamella of the PO projects to a zone (ventral lamella of PO zone) located between the rostrolateral MAO zone and the dorsomedial cell column zone.