Glial cell development and function in the rat optic nerve

This chapter discusses the development and properties of glial cells in the rat optic nerve, one of the simplest parts of the central nervous system (CNS). Some of these findings may prove to be helpful in understanding the role of glial cells in CNS regeneration. The rat optic nerve contains three types of macroglial cells—oligodendrocytes and two types of astrocytes. Type-1 astrocytes form the glial limiting membrane at the periphery of the nerve and type-2 astrocytes occupies the interior of the nerve and corresponds to fibrous or fibrillary astrocytes. In vitro studies suggest that the three types of macroglial cells arise by two distinct lineages: oligodendrocytes and type-2 astrocytes develop from a common, bipotential progenitor cell, whereas type-1 astrocytes develop from a different precursor cell. Type-1 astrocytes first appear at embryonic day 16 (E16), oligodendrocytes on the day of birth (E21), and type-2 astrocytes between postnatal days, 8 and 10 (P8–10).