The trigemino-olivary projection in the cat as studied with retrograde transport of horseradish peroxidase.

The trigemino-olivary projection was studied in cats which from a ventral approach were injected with horseradish peroxidase into various parts of the inferior olive. Retrogradely labelled cells of all sizes were present in all three divisions of the spinal sensory nucleus: nucleus caudalis, nucleus interpolaris and nucleus oralis. The projection is bilateral with the highest number of labelled cells on the contralateral side. No retrogradely labelled cells are found in the principal nucleus, but some cats showed a few retrogradely labelled cells within the ipsilateral mesencephalic nucleus. The findings are discussed and related to recent observations concerning the distribution of the direct trigemino-cerebellar fibres.