CELLS IN AND OUTSIDE THE MOTOR TRIGEMINAL NUCLEUS PROJECTING TO THE CEREBELLAR PARAMEDIAN LOBULE

To investigate afferent projections to the cerebellar paramedian lobul e (PML) from neurones in the motor trigeminal nucleus (Vmt) and the re gion around it, the method of retrograde transport of HRP, WGA-HRP and FG was employed in the rabbit. After tracer injection into various re gions of PML, labelled neurones were observed mainly in the ventral an d ventrolateral margins of the beta and gamma parts of Vmt, respective ly. In the region just outside Vmt, neurones were labelled mainly in t he lateral and dorsolateral parts of region 'h' and in the region adja cent to the root fibres of the facial nerve and even among them. Some neurones were recognized dorsally in region 'm' and in the pars alpha of the parvocellular reticular nucleus. The projection is sparse and b ilateral with a slight ipsilateral predominance. Neurones in Vmt send axons to PML sublobules b-f. Projection from regions around Vmt reache s all PML sublobules with sublobules e-f receiving more fibres.