Epigenetic control of vasopressin expression is maintained by steroid hormones in the adult male rat brain

The authors explored how steroid hormones affect methylation in the adult brain using a rat model. They castrated male rats, effectively removing their endemic source of testosterone. Testosterone exposure is necessary for the synthesis of vasopressin, so castration decreases vasopressin. However, castration also increases estrogen receptor α. They found that castration increased methylation of the vasopressin promoter and decreased the ERα methylation. These results suggest that the methylation of some steroid-responsive genes in the adult brain is maintained by the presence of circulating steroid hormones (in this case, testosterone).