EXPRESSION OF S100 PROTEIN IN THE VESTIBULAR NUCLEI DURING COMPENSATION OF UNILATERAL LABYRINTHECTOMY SYMPTOMS

In adult guinea pigs, unilateral labyrinthine lesions were inflicted b y chloroform injections into the middle ear. Immunoreactivity for S100 protein (S100) in the vestibular nuclei was studied during compensati on of lesion-induced postural asymmetry symptoms, i.e., nystagmus, asy mmetrical head position. 1 h after unilateral labyrinthectomy, increas ed levels of astroglial S100 immunoreactivity were found in the superi or vestibular nucleus and in the medial/lateral vestibular nucleus bor der region on the side contralateral to the deafferentation. Bilateral ly, the astrocytic S100 immunoreaction increased in the lateral vestib ular nuclei around Deiters neurons. Maximal expression of S100 was not ed 3 h after the lesion. Subsequently, it diminished. Our data reveal that transsynaptically altered neuronal activity induces an astrocytic reaction which provides increased levels of S100 to the local neuropi l. Calcium and zinc binding S100 proteins may play a functional role f or the neuroplasticity during vestibular compensation.