Project Summary Oral contraceptives (OCs) contain synthetic estrogen and progesterone and are prescribed to millions of women in the United States for some period during their reproductive years. OCs also are approved for use after onset of menarche, which is well before brain maturation is complete. Among adult women, imaging studies suggest that use of OCs is associated with changes in brain structure and function. It is likely that cellular level changes also occur in the brain with OC use, particularly during the neurobiologically dynamic adolescent/young adult years. Surprisingly, there are no studies investigating the potential impact of OCs on the developing female brain, establishing a critical need to determine the potential effects of synthetic hormones on early life brain biology. In this application, we propose to investigate neuron-derived exosome (NDE) microRNA (miRNA) as a neurobiological index. Exosomes are membrane-bound sacs that transport biologically active materials throughout the body to promote homeostasis and facilitate intercellular signaling. Exosomes are released by most tissues, including neurons, as routine physiology, easily crossing the blood brain barrier. Exosomes are also present in many different biofluids. Alterations to exosome characteristics have been associated with the pathophysiology of several cancers and neurodegenerative disorders (e.g., Alzheimer’s). It is hypothesized that differential expression of NDE miRNAs may aid identification of aberrations in biological pathway regulation as a function of OC exposure. To investigate the effect of OCs on early life neurobiology, NDE miRNA expression in young women prescribed OCs will be compared to natural cycling, OC naïve females. We will recruit 60 young women (15-22 years), including N=30 young women using OCs > 6 months and 30 natural cycling, OC naïve young women. This study will take advantage of the comprehensive Affymetrix GeneChip array to inventory miRNAs to index brain-based cellular perturbations. The OC use group will participate in two study visits, for a total of 60 person-time points while the natural cycling, OC naïve group will complete four study visits during the early follicular, late follicular, ovulation, and luteal phases for a total of 120 person-time points. As a first step, it will be necessary to understand whether NDE miRNA expression fluctuates as a function of hormonal milieu. Thus, Aim 1 will characterize NDE miRNA expression across the menstrual cycle while Aim 2 will determine whether NDE miRNA differs across the active and inactive pill phases. Finally, Aim 3 will characterize the NDE miRNA landscape in OC users. NDE miRNAs identified in Aim 3 also will be probed with complementary network- based analyses to identify involved neurophysiological pathways. Insights from this study will clarify whether there is scientific merit to proceed to in vivo studies as well as causally informative, longitudinal studies of OCs to elucida...