抄録
In a semi-natural habitat, female mice were much more aggressive than males in both wild type (WT) and oxytocin gene knockout (OTKO). Parallel single-unit recordings show that the proportion and responses of OT-responsive neurons in ventromedial hypothalamus (VMH) are sexually different in both WT and OTKO mice. Similarly, single-cell RT-PCR study revealed sexual difference in the expression pattern of a battery of PKC isozyme genes in rat VMH neurons co-expressing OT and estrogen receptors (ERs). Such corresponding sexual differences are also observed for reproductive behaviors. Adult male rats are much less responsive to E than females in the induction of lordosis and proceptive behaviors, even after castration and high doses of E in VMH. This sex difference can be seen in pups as young as immediately after weaning. Using single-cell RT-PCR, VMH neurons of such young pups had already shown sexual differences in the expression of genes for ERs and PKC isozymes. Even earlier, during the critical period of sexual differentiation, sexual differences in gene expression in preoptic area and VMH were found with our microarray study. Responses of genes may also differ; certain mRNAs are induced by E in the VMH of females but not males. Even a same gene, ERα, can mediate different types of reproductive behavior and can have opposite effects on aggressive behaviors in different sexes. We now apply patch clamp techniques to determine whether E can both promote inward and inhibit outward currents on male rat VMH neurons as it did on female,s. [Jpn J Physiol 54 Suppl:S40 (2004)]
