Immunolocalization of Androgen Receptors and Aromatase Enzyme in the Adult Musk Shrew Brain

Abstract

In the brain and other tissues, estrogens are produced by aromatization of androgens. Biochemical data suggest that aromatase enzyme is regulated by the androgen receptor (AR). Neurons that contain either AR or aromatase (AROM) enzyme reside in many of the same brain regions. In this report, we examined the codistribution of AR- and AROM-enzyme-immunoreactive (-ir) neurons in several regions of the adult male and female musk shrew brain. Data were collected from the intermediate nucleus of the lateral septum (LS), medial anterior (BNSTMA) and medial posterointerior (BNSTMP) divisions of the bed nucleus of the stria terminalis, medial preoptic area (mPOA), ventromedial nucleus of the hypothalamus (VMN), medial (MeA), cortical and central nuclei of the amygdala. Males had significantly more AR-ir neurons in the BNSTMP, mPOA, VMN and LS as compared to females. With the exception of the BNSTMA and LS, males had more AROM-ir neurons in each region than females. Furthermore, males had significantly more double-labeled neurons than females in the BNSTMP, mPOA, VMN, LS and MeA. The percentage of AROM-ir neurons that also contained AR immunoreactivity ranged from 13 to 82% depending on sex and region. The highest percentage of dual-labeled neurons (79% in females and 82% in males) was found in the VMN. Taken together, these data show that there is extensive cellular colocalization of AR and AROM enzyme in specific regions of the musk shrew brain. We propose that in both sexes, androgen receptors may act as transcription factors to regulate AROM enzyme.