Rapid estrogen regulation of DHEA metabolism in the male and female songbird brain

Abstract

In the songbird brain, dehydroepiandrosterone (DHEA) is metabolized to the active and aromatizable androgen androstenedione (AE) by 3β‐hydroxysteroid dehydrogenase/Δ5‐Δ4 isomerase (3β‐HSD). Thus, brain 3β‐HSD plays a key role in regulating the steroidal milieu of the nervous system. Previous studies have shown that stress rapidly regulates brain 3β‐HSD activity in a sex‐specific manner. To elucidate endocrine regulation of brain 3β‐HSD, we asked whether 17β‐estradiol (E₂) regulates DHEA metabolism in adult zebra finch (Taeniopygia guttata) and whether there are sex‐specific effects. Brain tissue was homogenized and centrifuged to obtain supernatant lacking whole cells and cell nuclei. Supernatant was incubated with [³H]DHEA and radioinert E₂in vitro. Within only 10 min, E₂ significantly reduced 3β‐HSD activity in both male and female brain. Interestingly, the rapid effects of E₂ were more pronounced in females than males. These are the first data to show a rapid effect of estrogens on the songbird brain and suggest that rapid estrogen effects differ between male and female brains.