Three sex dimorphisms in the granule cell layer of the hippocampus in house mice

Inbred strains of mice differ in number of neurons in the dentate granule cell layer of hippocampus and in granule cell density. In a study of both sexes in 6 strains, females had significantly lower granule cell density than males of the same strain. Females of strains with high neuron numbers had significantly fewer granule cells than males of the same strain, while males and females of low neuron number strains did not differ from each other. Sizes of neuronal nuclei were examined in males and females of two strains. No significant strain difference was found, but females had significantly smaller nuclei. The results suggest that hippocampal function is associated with the differing adaptive roles of male and female house mice.