Androgens and the androgen receptor (AR) both play critical roles for the development of the male phenotype. To investigate the roles of androgens in the developing nervous system, we examined the AR messenger RNA distribution by in situ hybridization. Our results indicate that AR transcripts were detectable in male mouse embryos at embryonic day 11 (E11). Intensive AR labeling appears in the neuroepithelium of brain vesicles and spinal cord, as well as in the reproductive organs. During E15–E16, new and strong AR labeling appeared in the cortex of cerebrum and hippocampus. Specific AR signals were also present in the brain areas known for hormonal control of copulatory behavior and mediating sensory processing. Interestingly, many ganglia were found to express AR mRNA at E15–E16. These novel AR-expressing sites include the dorsal root, sympathetic, and celiac ganglia, as well as the opthalmic nerve of trigeminal ganglion. Sex dimorphism of AR expression in brain was also observed during E15–E16. Postnatally, brain and spinal cord can respond to circulating androgen levels by modifying their AR gene expression, but the ganglia cannot. Together, these data suggest androgens may have a great influence on the development and maintenance of the nervous system through the AR.
