Project Summary The neurobiology of social behavior is of crucial importance not only in order to understand our own basic biology, but also for cases in which social behavior is impaired (for example, autism spectrum disorder and schizophrenia). The effects of social support on long-term health are now largely undisputed; and the dangers of loneliness are also increasingly well-recognized. For instance, a recent meta-analysis found that poor social relationships led to 29% increased risk for coronary heart disease, and a 32% increased risk for stroke. Our own prior investigations on the neurobiology of primate social bonds, like many others, have focused on males. Females represent a crucial and under-studied population when it comes to both psychiatric disorders of social behavior and studies of primate pair-bonding. Females are also more likely to be diagnosed with affective disorders, such as major depressive disorder, which may have critically understudied social risk factors, such as social stress. Here we propose a series of investigations into the neurobiological basis of attachment in female titi monkeys, a socially monogamous New World primate, using pharmacology and functional imaging to address fundamental questions about the substrates for sociality. Our overarching hypothesis is that the transition from attachment to parents to attachment to a pair-mate, may rely on neuropeptide receptor function, particularly the neuropeptides oxytocin and vasopressin. We will study these questions in adolescent and adult female titi monkeys. We will use behavioral pharmacology to investigate the effects of oxytocin and vasopressin manipulation on the fundamental traits of an attachment (preference for the partner/parent, distress upon separation, and social buffering). We use functional imaging to examine dynamic changes in glucose uptake in areas that we know to have oxytocin or vasopressin receptors in titi monkeys, in response to manipulations including the presence or absence of an attachment figure. Finally, we will use molecular techniques to examine changes in methylation of the oxytocin and vasopressin receptors across the course of pair-bonding, separation, and buffering from stress.