Study on remodeling of astrocytes in facial neuclus after peripheral injury

To observe the glial reactions surrounding facial motor neurons following facial nerve anastomosis. At 1, 7, 21 and 60 d following facial nerve anastomosis, the recovery process of facial movement was observed, the glial fibrillary acidic protein (GFAP) immunoreactivity was analyzed by a combined method of fluorescent retrograde tracing and immunofluorescent histochemical staining, and the ultrastructure of astrocytes were observed under a transmission electron microscope (TEM), respectively. Postoperatively the function of facial muscles could not return to normal, often accompanied with hyperkinetic syndromes such as synkinesis at the late stage. Motor neurons in every facial subnucleus could be retrogradely labeled by fluoro-gold (FG), and displayed an evident somatotopic organization. Normally there was a considerable number of GFAP-positive cells in nonnucleus regions but few inside the facial nucleus region. Postoperatively the GFAP immunoreactivity in the anastomotic side increased significantly, but gradually decreased at the late stage. The ultrastructure of astrocytes in our experiment showed that the sheet-like process of astrocytes invested and protected the injured facial motor neurons. The present study shows that reactive astrocytes undergo some characteristic changes during the process of facial nerve injury and regeneration. The plastic change at the late stage may be involved in the mechanism of synkinesis.