The central cervical nucleus in the cat. II. The cerebellar connections studied with retrograde transport of horseradish peroxidase.

After HRP injections in kittens and adult cats into parts of the cerebellum known to receive spinal afferents, retrogradely labelled neurones were found in the C1--C4 segments of the spinal cord, primarily in the central cervical nucleus (CCN). A few labelled neurones were also found in laminae IV and VI--IX of Rexed. The results obtained in kittens and adult cats were similar. Control HRP injections were made into the vestibular nuclei and the inferior colliculus. After injections mainly involving the vestibular nuclei a few faintly labelled neurones were found in the C1--C4 segments in, and occasionally also outside the CCN, in laminae VI--VIII. After injections into the inferior colliculus, however, no labelled neurones were observed in these segments. After spinal cord hemisections at C1 and bilateral HRP injections into the anterior lobe, nearly all labelled CCN neurones were found ipsilateral to the hemisections. Labelled axons of such CCN neurones could be traced across the midline to the lateral funiculus. A few neurones were found outside the CCN in laminae VII--IX. Contralaterally labelled neurones were found mainly in lamina VI.