Effects of changes in gonadal hormones on the amount of aromatase messenger RNA in mouse brain diencephalon.

Aromatase in brain is known to play a crucial role in development and maintenance of androgen dependent sexual behavior of males. Biochemical studies have shown that the aromatase activity in brain is influenced by androgen. In this study, we measured the aromatase mRNA content of mouse brain quantitatively to gain a deeper insight into this phenomenon. We found that in the diencephalic area it is sexually dimorphic, as reported for aromatase activity. The amount of aromatase mRNA in this area in males was 150% higher than that in females and decreased to the level in females after castration. The content of aromatase mRNA in castrated males was elevated by 2-fold by injection of testosterone and restored to the level observed in intact males. Injection of testosterone also affected the level of aromatase mRNA in normal mice of both sexes, though to lesser extent. On the contrary, injection of estrogen decreased the amount of aromatase mRNA in gonadectomized mice of both sexes. These results show that transcriptional control of the aromatase gene is involved in the mechanism of testosterone to affect sexual behavior.