Radial glia in the developing mouse cerebral cortex and hippocampus.

The regional distribution of radial glia in the developing cerebral cortex and the hippocampus of the mouse was studied using silver impregnation and immunocytochemical staining for glial fibrillary acidic protein (GFAP). Whilst the former technique revealed radial fibres at a slightly earlier age, immunocytochemistry gave a better picture of their general distribution and enabled systematic study of the appearance and disappearance of GFAP-positive radial glia throughout the cortex. Although a clear association between migrating neurones and radial glia was evident in the later stages of cortical plate formation, this relationship was not apparent in all cortical regions nor at the very early stages of the formation of the cortical plate. Even after allowing for a delayed appearance of GFAP immunoreactivity in relatively mature radial glia, the uneven distribution of these cells, their appearance after the cortical plate has already been formed, and their regional development in a pattern dissynchronous with that of the cortical plate argue against a general role of these structures in neuronal migration in the mouse, although there are notable phylogenetic differences.