Individual differences in induction of activity-dependent genes in Cnga2 -null mice after exposure to female mice. A. Expression of c-fos in mice which were sacrificed from their home cages without any odorant exposure. Significantly reduced expression levels of c-fos were observed in the OB (A1’) and AOB (A2’) of Cnga2-null male mice compared to that of wild type male littermates (A1, A2, respectively). B. Induction of c-fos expression in male mice which were exposed to estrous female mice. Arrowheads indicate the glomerular layer and arrows indicate the granule cell layer. Sexual stimulation by female mice induced expression of IEGs in the wild type OB (B1, B2). IEG induction was almost absent in the Cnga2 mutants which did not show sexual behaviors (B1’, B2’). IEG induction occurred in the OB, mainly in the granule cell layer, of the Cnga2-null male mice which showed sniffing and mounting behaviors (B1”, B2”). Insets in (B1-B2”) show magnified views of the boxed areas. IEG induction occurred in the AOB of male mice exposed to female mice (arrows, B3-B4”). (B5-B6”) Induction of IEGs in the PC (arrows) after exposure to female mice. Both in the wild type mice (B5, B6) and the mutants (B5”, B6”) which showed sexual behaviors, expression of IEGs was induced in the PC. IEG induction did not occur in the PC of Cnga2-null mice (B5’, B6’) which did not show sexual behaviors. (B7-B8”) Induction of IEGs in the MePD (arrows) after exposure to female mice. Both in the wild type mice (B7, B8) and the mutants (B7”, B8”) which showed sexual behaviors, expression of IEGs was induced in the MePD. The IEG induction did not occur in the MePD of Cnga2-null mice (B7’, B8’) which did not show sexual behaviors. Scale bars: (A1-A2’ and B3-B4”) 100 μm, (B1-B2”) 500 μm, (B5-B8’) 200 μm.