Axotomy of the Facial Nerve Not Only Induces Changes in the Facial Nucleus But Also in Remotely Related Brain Regions
It is well established that following lesion of the rats facial nerve, changes are found in its nuclar region involving motoneurons, their afferent synapses, microglia, and astroglia. Functional changes in remote brain regions such as the motor cortex have been reported shortly after lesion of a peripheral motor nerve (Sanes et al. 1988). Mechanisms involved are not yet well known. Such possible mechanisms might be important for comprehension of facial dyskinesias (hemifacial spasm, blepharospasm, synkinesis). In the present study we transected the right facial nerve in adult rats. To demonstrate reactions of glial and neuronal structures, we studied immunohistochemical changes in S100-protein glial fibrillary acidic protein (GFAP), and phosphorylated and nonphosphorylated neurofilaments in various brain regions and after various survival times. Following facial nerve lesion we not only found changes in the facial nucleus but also in remotely related brain regions, especially in the neocortex. These include quickly appearing side differences in the accumulation of glial markers (S100, GFAP).