Immunocytochemical demonstration of topographic ordering of Purkinje cell axon terminals in the fastigial nuclei of the rat.

We have used a monoclonal antibody, mabQ113, which selectively stains a subset of cerebellar Purkinje cells, to study the topography of the corticonuclear projection of the median vermis to the fastigial nuclei in the rat. The fastigial projection zone contains both mabQ113+ and mabQ113- Purkinje cells grouped into parasagittal bands. The immunoreactivity extends throughout the Purkinje cell including the axon terminals and thus it is possible to investigate the topographic distribution of mabQ113+ terminals. In the fastigial nuclei the target cells receiving mabQ113+ axon terminals are concentrated in the caudal pole. In the rostral pole, cells receive anti-GAD+ terminals but not mabQ113+ terminals. There is no gradient in anti-GAD staining. Double-labelling experiments with mabQ113, anti-GAD, and an antisynaptic antibody mabQ155 suggest that there is little or no mixing of mabQ113+ and mabQ113- Purkinje cell terminals on the same target neuron.