Persistence of spinocerebellar afferent topography following hereditary Purkinje cell degeneration.

Cerebellar Purkinje neurons play a significant role in the development and early maintenance of cerebellar afferent topography. Anterograde intra-axonal labeling experiments were designed to identify any role for Purkinje cells in maintaining spinocerebellar mossy fiber afferent topography in shaker mutant rats with adult onset Purkinje cell heredodegeneration. Following the death of Purkinje cells myelinated spinocerebellar axons persist and their terminal mossy fiber morphology remains normal in appearance and size. The relative percentage of labeled projections to each of the five anterior lobe lobules was comparable in mutant and normal rats. Finally, unfolded reconstructions of the anterior lobe illustrated that the organization of labeled terminals in clusters, patches and discontinuous parasagittally oriented stripes or transversely oriented bands were spatially distributed the same in both normal and mutant rats. These findings strongly infer that Purkinje cells are not necessary for the persistence and maintenance of spinocerebellar afferent pathways in adult animals.