Fig. 2.

NPAS1 and NPAS3 neurons colocalize with GABA. (A) Photomicrographs of brain sections subjected to double-labeling immunocytochemistry for NPAS1 and GABA (Left) and NPAS1 and GAD-67 (Right). (Left) The 10-μm paraffin section was taken from the hippocampus of a wt mouse. The NPAS1 reaction product in the nucleus was detected with the Vector DAB peroxidase substrate, whereas the blue-gray GABA reaction product in the cytoplasm was detected with the Vector SG peroxidase substrate. (Magnification, ×700.) (Right) This micrograph is a 40-μm vibratome section through the cerebral cortex of an NPAS1^–/– mouse stained for β-galactosidase. The blue, nuclear reaction product marks the presence of NPAS1. The section was then exposed to anti-GAD-67 (Chemicon, 1:1,500) followed by the Vector DAB peroxidase substrate to yield a brown, cytoplasmic reaction product. (Calibration bar, 20 μm.) (B) Photomicrographs from the CA1 (Upper) and CA3 (Lower) areas of the hippocampus from a wt mouse taken under fluorescent and bright-field illumination. The nuclear NPAS3 brown reaction product was detected with the Vector DAB peroxidase substrate kit. The fluorescent GAD-67-expressing neurons were detected by using Texas Red Avidin D (Vector Laboratories). Arrows indicate double-labeled neurons. (Calibration bar, 50 μm.)