Roles of estrogen receptor α and androgen receptor in the regulation of neuronal nitric oxide synthase

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Abstract
In brain and peripheral tissues, steroid hormones regulate nitric oxide synthase (nNOS). We asked whether estrogen receptor‐α (ERα) and/or androgen receptor (AR) regulated nNOS immunoreactivity in mouse brain. First, we quantified cells singly labeled for nNOS immunoreactivity or labeled dually with ERα‐immunoreactive (‐ir) or AR‐ir cells in the nucleus accumbens (Acb), preoptic area (POA), bed nucleus of the stria terminalis (BNST), posterior dorsal and posterior ventral regions of the medial amygdala (MePD and MePV, respectively), and paraventricular nucleus (PVN). The POA and MePD contained the greatest number of double‐labeled cells. More nNOS‐ir cells were colabeled with ERα immunoreactivity compared with AR immunoreactivity. Next, by using a double mutant mouse in which males lacked functional ERα, AR, or both, we investigated the roles of these steroid receptors in nNOS‐ir cell numbers and immunoreactive area staining under testosterone (T) and estradiol (E2) conditions. Our data show that functional ERα is correlated with more nNOS‐ir cells under T conditions and more immunoreactive area staining in the POA under both T and E2 conditions. However, ERα decreases nNOS‐ir cell number in the BNST under E2 treatment. In summary, the data suggest that AR has organizational actions on nNOS‐ir cell numbers in the MePV, that interactions between ERα and AR genes occur in PVN, and that sex differences in nNOS‐ir area staining are limited to the POA. Thus, we show that ERα and AR interact to regulate nNOS in male and female brain in a site‐specific manner. J. Comp. Neurol. 453:336–344, 2002.