AGE-RELATED-CHANGES IN GFAP-IMMUNOREACTIVE ASTROCYTES IN THE RAT VENTRAL COCHLEAR NUCLEUS

The age-related changes in the ventral cochlear nucleus (VCN) as revea led by glial fibrillary acid protein (GFAP) immunoreactivity were anal yzed in the following age groups: 3-, 6-, 12-, 18-, and 24-month-old S prague-Dawley rats. A cartographic and a quantitative analysis showed a significant increase in the number of GFAP positive astrocytes durin g the first year of life and a significant decrease in older rats. We also observed an age-induced modification in the spatial distribution of GFAP positive astrocyte. In the anterior part of the VCN of the 3- and 6-month-old rats, we observed a significant decrease in the rostro caudal as well in the dorso-ventral axes. In the posterior part of the VCN, a significant decrease in the dorso-ventral axis could be also o bserved, but no significant difference in the spatial distribution was obtained in the rostro-caudal axis. In older rats, the distribution a ppeared homogeneous throughout the nucleus. Additionally, aging was as sociated with a significant increase in GFAP positive astrocyte sizes, except for immunolabelled astrocytes in the granule cell layer. The d ifferent levels of GFAP expression occurring in the VCN during normal aging could reflect a progressive decline of cellular activity in the VCN, without severe cell degeneration or synaptic loss.