Dendritic pathology and overexpression of MAP2 in Purkinje cells from mice inoculated with rabies virus.

The effect of rabies virus infection on dendritic morphology and on the expression of the MAP2 protein in Purkinje cells in the cerebellum of mice was studied. ICR mice were inoculated with rabies virus, and six days later, the mice were sacrificed, the cerebellum was removed and processed for Golgi-Cox staining or MAP2 immunohistochemistry. Infection with rabies virus altered the dendritic pattern of Purkinje cells ranged from moderate changes to accentuated retraction in the dendritic tree of some Purkinje cells. The loss of dendritic branches in the samples of mice infected with RABV was also reflected in a decrease in intersections quantified using the Sholl technique, thus suggesting dendritic pathology. Immunoreactivity to MAP2 protein in the molecular layer of the cerebellum of control mice was mainly distributed in dendrites of Purkinje cells. Some somas were faintly stained. In infected mice immunoreactivity to MAP2 was intense in somas and dendrites of Purkinje cells and in some interneurons. These results are consistent with similar findings we previously reported for the cerebral cortex and spinal cord of rabies-infected mice. But they differ from studies in other pathologies where an association between dendritic pathology and loss of MAP2 immunoreactivity has been found. Our studies in rabies contribute to suggestion that MAP2 overexpression may also be associated with alterations in dendritic morphology. MAP2 protein contributes to maintaining cytoskeleton stability. However, in rabies, increased MAP2 expression here only determined by immunohistochemistry could destabilize the cytoskeleton of dendrites. Golgi staining is considered the gold standard for the study of dendritic morphology. Its association with changes in MAP2 expression appears to provide molecular support for the concept of dendritic pathology. These results contribute to the understanding of the effect of rabies virus infection on dendritic morphology. They therefore reinforce the idea that rabies not only has a dysfunctional effect on neurons, as some authors claim, but also affects their structure.