DISTRIBUTION OF GLIAL FIBRILLARY ACIDIC PROTEIN-IMMUNOPOSITIVE STRUCTURES IN THE BRAIN OF THE RED-EARED FRESH-WATER TURTLE - (PSEUDEMYS-SCRIPTA ELEGANS)

The distribution of glial fibrillary acidic protein (GFAP)-immunoreact ivity is described in serial Vibratome sections of the turtle brain. T he results are discussed in relation to our previous studies of rat an d chicken brains. In the turtle brain, the distribution of GFAP-positi ve elements is rather evenly abundant as compared to that observed in the chicken and rat. The GFAP-positive structures are fibers of differ ent length and orientation, but the stellate cells are not GFAP-positi ve. The basic systems is the radial ependymoglia, directed from the ve ntricles toward the outer surface of the brain. This system also conta ins some transverse and randomly oriented fibers. The cell bodies are not usually GFAP-positive. The large brain tracts could be recognized by their weak immunostaining, but gray matter nuclei could not be iden tified on the basis of immunostaining against GFAP. The layers of the optic tectum could be distinguished, as well as the gray and white mat ter of brain stem and spinal cord and the molecular and granular layer s of the cerebellum. In the cerebellum, a fiber system resembling the Bergmann-fibers, a strong midline raphe and coarse transverse fibers c ould be observed. These latter fibers have no equivalent in other cere bella. Their perikarya proved also to be GFAP-positive, and seemed to be dividing in the adult turtle brain. We conclude that the appearance of GFAP-positive stellate cells had a great importance in the evoluti on of avian and mammalian brains strengthening the thicker brain walls and assisting in the formation of local differences of GFAP-immunorea ctivity in different brain areas.