Quantitative analysis of rubral degeneration following neonatal deafferentation

The effect of neonatal hemicerebellectomy on the cytoarchitecture of the red nucleus was investigated in the rat. Quantitative analysis revealed a 31% loss of neurons in the magnocellular red nucleus contralateral to the lesion. This cell loss was accompanied by a similar decrease in the cross-sectional area of the red nucleus. To provide insight into this degenerative process, the neonatal status of the normal cerebellorubral projection was determined using anterograde transport of HRP-WGA which was injected into the deep cerebellar nuclei at various times during the first 10 postnatal days. A definitive cerebellorubral projection was not detectable before postnatal day 8. The data indicate that the rubral afferent fibers from the cerebellum were removed before they reached their target. These results are significant in light of the aberrant projections that develop after neonatal lesions.