Immunocytochemical demonstration of radial glia in the developing rat olfactory bulb with antibodies to glial fibrillary acidic protein.

Olfactory bulbs of 8-, 12-, 16- and 30-day-old rats were studied by means of immunocytochemistry using antibodies to glial fibrillary acidic protein (GFAP) and with the Toluidine blue-staining of semithin sections. Until day 12 the GFAP-reaction revealed a radial glia system, the fibres of which extended from the axial ventricular cleft to the surface. From day 16 onwards radial fibres were gradually replaced by typical astrocytes. The lack of proliferative activity within the bulb during the early postnatal period suggests that its cells are generated at and migrating from an external site. An intensely proliferating area was detected in the frontal lobe subventricular layer from where a bundle of migratory cells extends into the bulb. Radial glia may thus be of importance in guiding the migration of cells from this axial bundle to more peripheral regions of the olfactory bulb.