Increased glial fibrillary acidic protein immunoreactivity in astrocytes within the lateral vestibular nucleus of the cat following labyrinthectomy and vestibular neurectomy.

Unilateral vestibular injury evokes a characteristic pattern of acute disorganization of posture, locomotion, and eye movements. Following this acute stage, functional recovery occurs. In the present study, unilateral labyrinthectomy and vestibular neurectomy were performed in cats. The lateral vestibular nucleus (LVN) and vestibular nerve root entry zone on both sides of the brain stem were examined 24 hours, 3 days, and 8 weeks after operation by use of an immunochemical astrocyte marker, glial fibrillary acidic protein (GFAP). The results demonstrate extensive GFAP immunoreactivity within the ipsilateral nerve root following neurectomy, but not after labyrinthectomy. Prominent GFAP-immunoreactive astrocytic processes were detected in the LVN both ipsilateral and contralateral to neurectomy and labyrinthectomy. Within the ipsilateral LVN, the intensity of GFAP immunoreactivity was greater following neurectomy than after labyrinthectomy, but the pattern of GFAP reactivity remained similar. In the contralateral LVN, GFAP reactivity was noted exclusively in the dorsal-rostral region corresponding to the zone of cerebellar afferents to the LVN. The results of the present study suggest that reactive astroglia may play an important role in the mechanism that leads to vestibular compensation.