虽然雄性如何选择交配对象一直都是社交行为中被重点关注的问题，但科学家还未能从分子和细胞作用机制上解释哺乳动物性取向。

北京大学生命科学学院院长饶毅教授课题组通过研究发现，神经递质五羟色胺（5-HT，又称血清素）在哺乳动物性取向中具有重要作用。野生型雄性小鼠的正常性取向为雌性，虽然缺少中枢血清神经元一般不会导致小鼠嗅觉和信息素感应功能出现缺陷，但小鼠的性取向会因此丧失。该研究通过将大脑中5-HT合成第一步所需要的色氨酸羟化酶2（Tph2）从小鼠中敲除，以考察5-HT的作用。在实验中，研究人员往小鼠体内注射中间体5-羟基色氨酸（5-HTP）（该物质可绕过Tph2将5-HT恢复到野生型小鼠的正常水平），35分钟后，Tph2被敲除的小鼠性取向恢复正常。研究人员由此得出结论，在成体大脑中的5-HT和血清神经元可能对哺乳动物性取向具有调控作用。

该研究于3月23日在线发表在《自然》杂志上。

原文出处：

Nature  doi:10.1038/nature09822

Molecular regulation of sexual preference revealed by genetic studies of 5-HT in the brains of male mice

Yan Liu,1, 2, 6 Yun’ai Jiang,1, 3, 6 Yunxia Si,1 Ji-Young Kim,4 Zhou-Feng Chen4 & Yi Rao1, 5

Although the question of to whom a male directs his mating attempts1, 2 is a critical one in social interactions, little is known about the molecular and cellular mechanisms controlling mammalian sexual preference. Here we report that the neurotransmitter 5-hydroxytryptamine (5-HT) is required for male sexual preference. Wild-type male mice preferred females over males, but males lacking central serotonergic neurons lost sexual preference although they were not generally defective in olfaction or in pheromone sensing. A role for 5-HT was demonstrated by the phenotype of mice lacking tryptophan hydroxylase 2 (Tph2), which is required for the first step of 5-HT synthesis in the brain. Thirty-five minutes after the injection of the intermediate 5-hydroxytryptophan (5-HTP), which circumvented Tph2 to restore 5-HT to the wild-type level, adult Tph2 knockout mice also preferred females over males. These results indicate that 5-HT and serotonergic neurons in the adult brain regulate mammalian sexual preference.