Lack of Serotonin Influences Sexual Preference in Mice

The brain chemical serotonin may play a surprising role in sexual preference, according to a new U.S. study released Wednesday, which showed that male mice lacking serotonin began wooing other males with love squeaks and made attempts to mate with them, Science News reported.

The research involved using mice genetically engineered to lack serotonin-producing cells. They still courted females, but they no longer exclusively sought the attention of the ladies. When both male and female mice were present, about half the serotonin-lacking mice mounted the males first. They were also more likely to direct quiet love sounds to the males than to the females.

Some of the sexual behaviors were reversed after they were given an injection of a compound that restored serotonin to their brains.

"Nobody thought that serotonin could be involved in this kind of sexual preference," Zhou-Feng Chen of Washington University School of Medicine in St. Louis told Science News.

Serotonin is a neurotransmitter that is connected to many behaviors and may play a role in cognitive processes, including moods. Several antidepressants increase the amount of serotonin in the brain and can have sexual side effects, typically leading to a decrease in libido. There is no evidence that they influence sexual orientation.

The researchers have not yet looked at how serotonin might affect the sexual preferences of female mice. They further cautioned that the behavior of the mice cannot be extrapolated and applied to humans.