P0-P21 and adult rat brains were processed for expression of CR (see Methods). (A) P0, (B) P1, (C) P2, (D) P4, (E) P7, (F) P10, (G) P14, (H) P17, (I) P21 and (J) Adult. Arrowhead – CR-positive cells with weakly stained soma and no neurite staining, arrows – CR-positive cell with densely stained soma and neurites, CC – corpus callosum, I-V - approximate location of layers, scale bar is 50 μm.