reelin-expressing cells in the derivatives of the cortical plate and in the adult cerebral cortex and hippocampus are GABAergic nonpyramidal neurons. A, B, Distribution of reelin mRNA (blue, open arrows) and calretinin immunoreactivity (brownin A) or calbindin immunoreactivity (brown in B) in cortical layers IV and V of the neocortex at P5; double-labeled neurons are marked bybold arrows; calretinin-positive pyramidal neurons (thin arrows) do not express reelintranscripts. B, C, reelin-positive/calbindin-positive neurons in layer V at P5 display nonpyramidal shapes (bold arrows). A calbindin-immunoreactive neuron is labeled by athin arrow. D–F, Photomicrographs of the layer II–III of the neocortex at P21 showing reelinexpression (blue color, open arrows) and immunostaining (brown, thin arrows) for calretinin (D), neuropeptide Y (E), and somatostatin (F); double-labeled nonpyramidal neurons are indicated by bold arrows. G, H, Pair of photomicrographs taken at different planes of focus showing colocalization of reelin mRNA (silver grains in G, open arrows) and GAD67 mRNA (blue cells) at P21 in layer V of the neocortex; bold arrows point to double-labeled cells.I, Colocalization of reelin mRNA (blue) and calretinin immunoreactivity (brown) in the hippocampus at P21. Double-labeled neurons in the stratum oriens are labeled by bold arrows. SO, Stratum oriens; SP,stratum pyramidale; IV, V, cortical layers. Scale bars, 50 μm.