S100 and GFAP immunoreactivity of astroglia in the Diplodus sargus brain.

S100β protein and glial fibrillary acidic protein (GFAP) are widely distributed in astrocytes1 but also in ependymal and radial glia1. These proteins are then used as reliable markers of all astroglial cells. In teleost fishes, the studies on the astroglia are still relatively scarce. In this paper we report the study on the astroglial architecture in the brain of a teleost fish, Diplodus sargus, by the immunohistochemical staining of S100β protein and GFAP. The immunodetection of GFAP and S100 showed the presence of an astroglial architecture various in the sargus brain. It was represented mainly by radial glia and fibres, which were more numerous and large in the mesencephalon and rhombencephalon, but very scarce in the telencephalon. In fact in this region we revealed few and thin fibres immunoreactive only to anti-GFAP. In the other regions of the brain indeed we observed structures both GFAP(+) and S100(+). The immunodetection of these protein revealed generally a major number of GFAP(+) structures occasionally also S100(+). However, the immunolabeling of GFAP was more strong than the S100 immunolabeling. Radial glia was especially evident in the optic tectum and in the white matter of the cerebellum. The occurrence of bundles of GFAP(+) fibres, but also S100(+), was observed in the periventricular region, in the inferior lobes of the hypothalamus, in the dorsal thalamus and in the optic tectum. The infudibular region and the neurohypophysis showed also intensely GFAP(+) fibres, processes of the pituicytic cells, which appeared also S100(+).