Topography and axonal collaterals of trigeminocerebellar projection to the paramedian lobule and uvula in the rabbit cerebellum

To study projections of the trigeminal sensory nuclei (TSN) to the rostral parts of the paramedian lobule (PML) and of the uvula of the rabbit cerebellar cortex, the retrograde double fluorescent labeling method was used. Injections of Fast Blue (FB) into PML and Diamidino Yellow (DY) into the uvula, resulted in prominent labeling neurons with FB bilaterally and with DY ipsilaterally, in the principal trigeminal nucleus, subnucleus oralis, and rostral and caudal subnucleus interpolaris. We observed topographical arrangement of neurons in such a fashion that FB labeled cells were localized in the medial and DY labeled cells in the lateral regions of TSN. Apart from this small number of double FB+DY labeled neurons (n = 138) were found in the narrow common region of single labeling. This implies that PML and the uvula receive independent trigeminal sensory information from neurons in separate regions of TSN. However, some trigeminal neurons may also exert simultaneous influences upon these hemispheral and vermal components by way of axonal branchings.