Experts at Northwestern University have pinpointed the site of male sexual desire in the brain. Using a mouse model, the team demonstrated that sexual behavior among males is controlled by brain tissue that contains the gene aromatase.
This particular gene converts testosterone to estrogen in the brain, which drives male sexual activity. Prior to this research, the full function of aromatase was not known.
The researchers said that since aromatase regulates sexual behavior in men, it can be targeted by drugs to either increase its function for low sexual desire or decrease its function for compulsive sexual desire.
Study senior author Dr. Serdar Bulun is the chair of Obstetrics and Gynecology at Northwestern University Feinberg School of Medicine and Northwestern Medicine.
“This is the first key finding to explain how testosterone stimulates sexual desire,” said Dr. Bulun. “For the first time, we demonstrated conclusively that the conversion of testosterone to estrogen in the brain is critical to maintain full sexual activity or desire in males. Aromatase drives that.”
When aromatase was selectively knocked out in brain tissue, sexual activity in male mice decreased by 50 percent, despite the fact they had higher levels of testosterone circulating in their blood compared with normal mice.
“Male mice partially lost interest in sex,” said study co-author Dr. Hong Zhao. “Aromatase is the key enzyme for estrogen production. Estrogen has functions in males and females. Testosterone has to be converted to estrogen to drive sexual desire in males.”
Dr. Bulun said that if a normal male mouse is put with a female one, it would chase after her and try to instigate sex. “If you knock out the aromatase gene in the brain, their sexual activity is significantly reduced. There is less frequency of mating. The male mice are not that interested.”
According to the researchers, the finding can contribute to new treatments for disorders of sexual desire. For example, hypoactive sexual desire disorder is a common condition that can be a side effect of widely used medications such as antidepressants. A treatment to boost aromatase in this disorder could heighten sexual desire, said Dr. Bulun.
By contrast, compulsive sexual desire is another condition that can be treated by an existing systemic aromatase inhibitor, but that treatment has side effects such as osteoporosis. Dr. Bulun said that now, new selective drugs that suppress only the brain promoter region of the aromatase gene can be developed to eliminate such side effects.
The study is published in the journal Endocrinology.