Distribution of androgen receptor mRNA in the prepubertal male and female mouse brain

Androgens are steroid hormones that play a critical role in brain development and sexual maturation by acting upon both androgen receptors (AR) and estrogen receptors (ERα/β) after aromatization. The contribution of estrogens from aromatized androgens in brain development and the central regulation of metabolism, reproduction, and behavior is well defined, but the role of androgens acting on AR has been unappreciated. Here, we map the sex specific expression of Ar in the adult and developing mouse brain. Postnatal days (PND) 12 and 21 were used to target a critical window of prepubertal development. Consistent with previous literature in adults, sex‐specific differences in Ar expression were most profound in the bed nucleus of the stria terminalis (BST), medial amygdala (MEA) and medial preoptic area (MPO). Ar expression was also high in these areas at PND 12 and 21 in both sexes. In addition, we describe extra‐hypothalamic and extra‐limbic areas that show moderate, consistent and similar Ar expression in both sexes at both prepubertal time points. Briefly, Ar expression was observed in olfactory areas of the cerebral cortex, the hippocampus, several thalamic nuclei, and cranial nerve nuclei involved in autonomic sensory and motor function. To further characterize forebrain populations of Ar expressing neurons and determine whether they also coexpress estrogen receptors, we examined expression of Ar, Esr1 and Esr2 in prepubertal mice in selected nuclei. We found populations of neurons in the BST, MEA and MPO that coexpress Ar, but not Esr1 or Esr2, whereas others express a combination of the three receptors. Our findings indicate that various brain areas express Ar during prepubertal development and may play an important role in female neuronal development and physiology.