Table 4.

Cell-type composition, location, and levels of BrdU labeling in two-cell clusters

  • Data from 36 cortical hemispheres of 2-week-old rats given injections of retrovirus and BrdU at E16 are reported here.

  • Cells were studied either in double-immunostained cryostat sections orain adjacent semithin sections. Two-cell clusters are defined as pairs of β-gal+ cells located within 540 μm in both rostrocaudal and mediolateral dimensions. A cluster extending for >540 μm is marked with an asterisk.

  • F4-b Clusters that include cells located in different layers.

  • F4-c Clusters that include cells with different phenotype. Cortical areas were defined according to Paxinos and Watson (1986); laminar location was assigned according to Krieg (1946). Cells were classified as pyramidal neurons (Py) or nonpyramidal neurons (NP) according to morphological features, which included size and shape of the cell body and cellular processes, axonal morphology when applicable, and nuclear size and shape (Peters and Jones, 1984). In semithin sections, cells were classified on the basis of their immunoreactivity for GABA or glutamate. For the level of BrdU-immunoreactive nuclear area: ✺ = 25–50%;    = 12–25%;    = <12%.