Table 1.

Cell-type composition, location, and degree of BrdU labeling in horizontal clusters of β-gal+cells

  • 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. Horizontal clusters are defined as groups of β-gal+ cells located predominantly in the same layer and within 540 μm in both rostrocaudal (R-C) and mediolateral (M-L) dimensions. Clusters extending for >540 μm are marked with an asterisk.

  • F1-b Clusters including one cell located in a different layer. Cortical areas (FPM, fronto-parieto-motor cortex; FPSS, fronto-parieto-somatosensory cortex; AC, anterior cingulate cortex) were defined according to Paxinos and Watson (1986); laminar location was assigned according to Krieg (1946). Cells were classified as pyramidal neurons (Py) according to morphological features, which included size and shape of the cell body and dendritic 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 glutamate. For the level of BrdU immunoreactive nuclear area: ✺ = 25–50%;  = 12–25%;   = <12%; ? = unknown.