The origin and termination of the dentatorubral fibres in the cat as studied with retrograde and anterograde transport of peroxidase labelled lectin.

The dentatorubral projection in the cat was studied by means of retrograde and anterograde transport after implantations of crystalline wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the red and dentate nuclei, respectively. Our retrograde transport findings give evidence that rubral afferents originate in the contralateral dentate nucleus, mainly dorsally in its central part. The dentate implantations (with no contamination of the adjacent interposed nuclei) show that in the cat the great majority of the dentatofugal fibres leave the ipsilateral brachium conjunctivum to decussate below the red nucleus. Scattered crossing fibres also penetrate the contralateral red nucleus at all caudorostral levels on their way to the contralateral thalamus. Terminal fibres were found only in the rostral part of the red nucleus, but no retrogradely labelled rubral cells were observed. The findings are discussed in relation to previous studies on the dentatorubral projection.