Control of Cell Number in the Bed Nucleus of the Stria Terminalis of Mice: Role of Testosterone Metabolites and Estrogen Receptor Subtypes

Introduction. The bed nucleus of the stria terminalis (BNST) exhibits several sex differences that may be related to male sexual behavior and gender identity. In mice and rats, sex differences in the principal nucleus of the BNST (BNSTp) are due to sexually dimorphic cell death during perinatal life. Although testosterone treatment of newborn female rats increases BNSTp cell number, the relevant hormone metabolite(s) are not known, and the effect of testosterone on the development of BNSTp cell number in mice has not been examined. Aim. To identify the sex hormone metabolites and receptors controlling cell number, volume, and cell size in the BNSTp of mice. Methods. In the first experiment, C57BL/6J male mice were injected on the day of birth with peanut oil; females were injected with testosterone propionate (TP), estradiol benzoate (EB), dihydrotestosterone propionate (DHTP), or oil alone, and the BNSTp of all animals was examined in adulthood. In the second experiment, to compare effects of EB to the effects of estrogen receptor subtype specific agonists, newborn female mice were injected with EB, propyl-pyrazole-triol (PPT, a selective estrogen receptor alpha [ER alpha] agonist), or diarylpropionitrile (DPN, a selective estrogen receptor beta [ER beta] agonist). Main Outcome Measures. Nuclear volume measurements and stereological cell counts in the BNSTp in adulthood. Results. TP treatment of newborn females completely masculinized both BNSTp volume and cell number. EB masculinized neuron number, whereas DHTP had no effect on volume or cell number. In the second experiment, EB again fully masculinized neuron number in the BNSTp and in this study also masculinized BNSTp volume. PPT and DPN each significantly increased cell number, but neither completely mimicked the effects of EB. Conclusions. We conclude that estrogenic metabolites of testosterone control sexually dimorphic cell survival in the BNSTp and that activation of both ER alpha and ER beta may be required for complete masculinization of this brain region. Hisasue S, Seney ML, Immerman E, and Forger NG. Control of cell number in the bed nucleus of the stria terminalis of mice: Role of testosterone metabolites and estrogen receptor subtypes. J Sex Med 2010;7:1401-1409.