Distribution of Astroglial Lineage Cells in Developing Chicken Telencephalon from Embryo to Young Chick

The largest area of the avian telencephalon (Tc) is the subpallium [basal ganglia (BG)], and the pallium (cortex) is a narrow area located at the surface of the Tc. However, recent studies have proposed that most of the area of the avian Tc is the pallium, which corresponds to the cerebral cortex of mammals. This theory is based on neuronal elements with little regard to glial cells, which play important roles in neurogenesis. In the present study, we observed the distribution of glial cells using immunohistochemistry during maturation and discuss the division of the Tc by glial elements. In the early stage, the distribution and morphology of vimentin-positive radial glial cells were different between dorsal and ventral areas when they began to spread their processes toward the pia matter. During the development stage, vimentin-positive long processes divide the pallium and BG by the lamina pallio-subpallialis. Moreover, the pallium was divided into four regions by vimentin and glial fibrillary acidic protein-positive elements in the later stage.