Abstract
In the hypothalamus, there are two sexually dimorphic nuclei, the anteroventral periventricular nucleus (AVPV) and the sexually dimorphic nucleus of the preoptic area (SDN-POA), which have been associated with sex-specific regulation of reproductive neuroendocrinology and behavior. The AVPV is sexually dimorphic with over three times as many dopaminergic neurons in the female rat compared with male. On the other hand, the volume of the SDN-POA is several times smaller in female than in male. Estrogen, derived from circulating testosterone from pup testis, masculinizes the developing AVPV and SDN. However, molecular mechanisms of estrogen signaling in the sexual differentiation of the brain have not been clarified hitherto. In this report, using a customized DNA microarray with selected estrogen-responsive genes (172 genes), we attempted to show the gene cascades to establish the sexual dimorphism in the AVPV and SDN of rat brain. Several genes of the postnatal day 5 (PD5; the day of birth: PD1) female brain were up- or down- regulated, significantly, by masculinization with estrogen treatment on PD1. Six of these genes showed the same expression pattern between the AVPV and SDN. We are currently investigating estrogen-responsive gene expressions in the PD1–PD4 female brains to profile estrogen function. The data would contribute to clarify the molecular mechanisms of estrogen signaling in the sexual differentiation of the brain. [J Physiol Sci. 2006;56 Suppl:S217]
