Puberty and Brain Sexual Differentiation: Getting Organized

Abstract

The adolescent brain undergoes substantial remodeling and is a target of pubertal gonadal steroid hormones. Our work in the Syrian hamster shows that when gonadal hormones are absent during adolescent development, male-typical social behaviors are impaired. In contrast, when present during adolescent development, gonadal hormones program sex-typical adult social behaviors by organizing the adolescent brain. Using rats, we found that during puberty, new cells, including neurons and glia, are added to sexually dimorphic cell groups in the brain. The anteroventral periventricular area (AVPV) is larger in females than in males and is essential for the cyclic production of ovarian hormones. The sexually dimorphic nucleus (SDN) and medial amygdala (ME) are larger in males and functionally linked to male sexual behavior and processing of social sensory stimuli. During puberty, more new cells are added to the male than to the female SDN and ME, whereas more new cells are added to the female than male AVPV. Importantly, prepubertal gonadectomy obliterates these sex differences. Hormone-modulated addition of new cells to hypothalamic and limbic cell groups may be an active mechanism for preserving sexual dimorphisms during remodeling of the adolescent brain or for establishing new functional and behavioral sexual dimorphisms that emerge with adolescent development.