Cerebellar afferences from the mesencephalic trigeminal nucleus in the rat

The aim of the present study was to test for and characterize the organization of a direct projection from neurones of the trigeminal mesencephalic nucleus (Vme) to the cerebellum. WGA-HRP was used as a retrograde tracer following injections in the cerebellar cortex. The extent of each injection site within the sagittal zones was determined according to corticonuclear and olivocortical connections. Retrogradely labelled neurons were observed in the caudal part of the ipsilateral Vme only following vermal injection. The Vme projections reached exclusively the ipsilateral sagittal zone X in the anterior lobe, lobule VI and lobule IX. This identification was confirmed by anterograde labelling of mossy fibre terminals following a biocytin injection restricted to the Vme.