Evidence for the existence of an estrogen-responsive sexually dimorphic group of cells in the medial preoptic area of the 129SvEv mouse strain

The current study describes the presence of sexually dimorphic cell groups within the MPO of the 129SvEv, but not the C57BL/6J strain of mice. We detected galanin-positive clusters of cells located in the MPO of 129SvEv and C57BL/6J mice, with sex differences found only in the 129SvEv strain. Aromatase-positive and dense Nissl-counterstained clusters of cells were identified only in the MPO of 129SvEv mice, but not in the C57BL/6J strain. Furthermore, this study has demonstrated that the volume of these sexually dimorphic cell groups is regulated by estrogen, but not testosterone, as male aromatase knockout mice (which have high levels of testosterone, but no estrogen) show reduced cell group volumes. These structural changes, which occur in an estrogen-deficient state may influence male sexual behaviors.