Sex- and age-related differences in c-fos expression in dog olfactory bulbs

Sex- and age-related differences in cognitive abilities are frequently reported. However, the sex- and age-related differences in dog olfaction due to biological system are still poorly understood. We examined c-fos expression in dog olfactory bulbs by immunohistochemistry approaches. The c-fos is mainly expressed in the olfactory glomerular layer (GL), mitral cell layer (ML) and granule cell layer (GRL). We found that a higher density of c-fos-positive cells could be detected in the ML of olfactory bulbs of adult female dogs compared with that in males and the c-fos-positive cells in females' olfactory bulbs are more distinct. Sex-related differences in c-fos expression also appeared in the GL of olfactory bulbs in juvenile dogs. We also discovered that the density of c-fos-positive cells in the GRL of adult dogs was much higher than that in the GRL of juvenile dogs. Our results indicate that cells in the olfactory bulbs of female dogs are more active than those in males and female dogs may have much stronger ability for long-time memory of odours than male dogs. Furthermore, our results also suggest that adult dogs may have much stronger ability for long-time memory of odours and can deal with more complicated odour information than juvenile dogs.