Astrocyte reaction in the rat vestibular nuclei after unilateral removal of Scarpa's ganglion

Unilateral vestibular ganglionectomy (UVG) results in a complete degenerati on of vestibular nerve fibers and terminals in the ipsilateral vestibular n uclear complex (VNC). A subsequent glial reaction may affect the activities of VNC neurons and thereby influence compensation for lesion-induced vesti bular disorders. Expression of glial fibrillary acidic protein (GFAP), a sp ecific marker for reactive astrocytes, was demonstrated immunohistochemical ly in the rat VNC at 7, 14, and 35 days after UVG. An increased GFAP-positi ve astrocytic response was evident at 7 days after lesion in all the VNC re gions on the lesioned side and in some regions on the unlesioned side and r emained through 35 days. The glial response included hypertrophy, which was more prominent at 7 days than at 14 days or 35 days, and proliferation, mo re prominent at the later times, of GFAP-positive astrocytes. Astrocytic pr ojections around VNC neuron somata and proximal dendrites increased in numb er and became thicker and more elongated, especially at 14 days, in the lat eral vestibular nucleus. It is suggested that UVG results in a bilateral as trocytic reaction in the VNC that would affect the subsequent compensation.