Discussion: Neopallial Wall

The methods which were used in this study (Astrom and Webster 1990) have allowed us to examine whole brains of fetal rats in an early period of development (E11–13) and to use light and electron microscopy for studies of well-preserved cells within selected areas of the pallial wall. During this time period the selected regions (the neopallial wall and the area choroidea) have the same basic structure, which is that of a pseudostratified neuroepithelium. Like authors of previous studies, we found that the neuroepithelial cells are radially oriented and have an asymmetrical shape (His 1889; Sauer 1935b). They are joined by junctional complexes near the ventricles (Duncan 1957), they extend through the wall to the pial surface where the outer ends are covered by a basal lamina, and they have cytoskeletons composed of axial microtubules and microfilaments (Lyser 1964, 1968; Herman and Kauffman 1966). We have also confirmed previous observations on the fine anatomy of the columnar/radial glial cells in the telencephalic wall of mice (Meller et al. 1966; Hinds and Ruffett 1971; Choi 1988), in rats (Matsuyama et al. 1973; Peters and Feldman 1973; Rickmann and Wolff 1985), and in rabbits (Stensaas and Stensaas 1968). Earlier studies are concerned mainly with the radial glial cells which appear during the period of neuronal migration. This project is different in that it deals only with the columnar cells which are seen in the preneuronal period.