A chemical in the brain controls sexual preference in mice

Male mice bred without serotonin lose their preference for females. The researchers say it is the first time that a neurotransmitter has been shown to play a role in sexual preference in mammals. The research team first bred male mice whose brains were not receptive to serotonin. A series of experiments demonstrated that these mice had lost the preference for females shown by unmodified males. When presented with a choice of partners, they showed no overall preference for either males or females. When just a male was introduced into the cage, the modified males were far more likely to mount the male and emit a mating call normally given off when encountering females than unmodified males were. Similar results were achieved when a different set of mice were bred. These lacked the tryptonphan hydroxylase 2 gene, which is needed to produce serotonin. However, a preference for females could be restored by injecting serotonin into the brain.