RT Journal Article SR Electronic T1 Fibrous and protoplasmic astrocytes are biochemically and developmentally distinct JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 585 OP 592 DO 10.1523/JNEUROSCI.04-02-00585.1984 VO 4 IS 2 A1 RH Miller A1 MC Raff YR 1984 UL http://www.jneurosci.org/content/4/2/585.abstract AB We have studied semithin frozen sections of developing and adult rat central nervous system (CNS) by indirect immunofluorescence in order to determine the antigenic phenotype of protoplasmic and fibrous astrocytes. Using antibodies against glial fibrillary acidic protein (GFAP) to identify astrocytes, we show that the great majority of fibrous astrocytes in adult optic nerve are labeled by the monoclonal antibody A2B5, while the great majority of protoplasmic astrocytes in adult cerebral cortex are not. Astrocytes located at the periphery of the adult optic nerve that form the glial limiting membrane are more like protoplasmic astrocytes than fibrous astrocytes in that they strain relatively weakly with anti-GFAP antiserum and are A2B5-. In the developing rat optic nerve, protoplasmic-like astrocytes appear at least one week before the first fibrous astrocytes can be detected. Taken together with our previous observations on astrocytes in suspensions and cultures of developing rat optic nerve (Raff, M.C., E.R. Abney, J. Cohen, R. Lindsay, and M. Noble (1983) J. Neurosci. 3: 1289–1300; Raff, M.C., R.H. Miller, and M. Noble (1983) Nature 303: 390– 396), these results suggest that protoplasmic and fibrous astrocytes are distinct classes of glial cells that differ in their antigenic phenotype and developmental history, as well as in their morphology and location within the CNS.