Neuroendocrine Mechanisms Regulating Adolescent Social Development

Adolescence is a time of remarkable development in social, emotional, and cognitive abilities. However, it is also a time of increased vulnerability to mental health disorders and increased sensation seeking thought to underlie an elevated incidence of deaths and injuries from accidents. These behavioral changes are accompanied by complex interactions between hormones and the brain, and a major challenge is to parse out which neural and hormonal factors are responsible for adolescent behavioral changes and which merely coincide with them. Activation of pubertal hormones in adolescence is the primary candidate. In this research project, a new model is introduced that makes use of a seasonally-breeding hamster species, for which the timing of puberty can be controlled simply by manipulating day length -- hamsters born and raised in long, summer-like day lengths undergo puberty early, whereas those born in short, winter-like day lengths delay puberty by several months in order to prevent breeding during the harsh winter months. The proposed experiments use this model to test the role of pubertal hormones in adolescent social behavioral and neural development. This research will advance understanding of the neural and hormonal factors that both drive adolescent social development and underlie the increased vulnerability of this life stage. An additional part of this project is the principal investigator's oversight of a student-run outreach program with the Buffalo Zoo to create zoo camps designed to spark children's interest in the sciences. The inclusion of University student participation promotes and provides training in science outreach and early childhood science education. This project tests the role of pubertal hormones in adolescent behavioral and neural development, focusing on play behavior, the predominant social behavior in adolescent animals, and the 'social' vasopressin (VP) pathway, a pathway recently implicated in adolescent social development. The goal of Aim 1 is to determine the role of pubertal hormones in the development of the 'social' VP pathway. Its neuroanatomical development in the hamster model is being uncovered using immunohistochemistry and in situ hybridization. Aim 2 serves to determine the projections through which the 'social' VP pathway regulates play. The role of four key projection areas is being tested with site-specific infusions of a VP agonist and antagonist to determine how this pathway regulates social development. Aim 3 involves an initial test of the role of estradiol in early adolescent behavior. Estradiol levels are measured using enzyme immunoassay in the hamster model to determine whether day length impacts circulating estradiol levels in juvenile hamsters. This research program will begin to map puberty-dependent and puberty-independent neural circuits and specify how they interact to regulate adolescent social development. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.