ABSTRACT
This study examined the distribution and regulation of androgen receptor immunoreactivity (IR) in the brain of the hypogonadal (hpg) male mouse, genetically deficient in GnRH. Five groups of animals were studied: intact, castrated, or castrated and testosterone propionate (TP)-treated normal adult male mice, and intact or TP-treated hpg adult male mice. All groups were studied 1 week after treatment. Five regions of the brain with high concentrations of androgen receptors in normal animals were examined, including the medial preoptic area, the lateral ventral septum, the ventromedial hypothalamus, the bed nucleus of the stria terminalis and the medial amygdala. The results showed that the congenital absence of GnRH results in minimal expression of androgen receptor-IR in mice in all regions examined. However, treatment with exogenous testosterone for 1 week was sufficient to induce the numbers of neurons containing androgen receptors, as detected by immunocytochemistry, into the range seen in normal male mice in all the areas studied except the VMH. Similar plasticity was also observed in normal males after 1 week of castration and TP replacement.