PROJECT SUMMARY While there is a high prevalence for the co-occurrence of alcohol use disorders (AUD) and post-traumatic stress disorder (PTSD), the mechanisms underlying these disorders are not fully understood. Further, few treatments are effective for those suffering with PTSD-AUD comorbidity. Animal models that closely mimic the key clinical features of these disorders are critical for elucidating mechanisms and factors that underlie the co-occurrence of these illnesses and facilitate development of new and more effective therapeutics. We have recently conducted a series of pilot studies with the goal of developing such a model. Specifically, we have demonstrated that chronic predator odor (TMT) exposure sensitizes male and female mice to later acute stress (TMT)-induced reinstatement of alcohol relapse-like behavior. This effect is long lasting (>60 days) and the sensitized effect generalizes to exposure to context cues associated with prior chronic TMT exposure. We have also demonstrated that a novel model of chronic early-life stress (CES) has long-lasting effects on anxiety behavior and stress responsiveness, as well as increased stress-related alcohol consumption. Finally, our pilot work shows that chronic TMT exposure produces long-last alterations in oxytocin (OT) expression in hypothalamus (PVN) as well as oxytocin receptor mRNA expression in stress-relevant projection brain regions (central amygdala; CeA, bed nucleus of stria terminalis; BNST). Further, systemic administration of OT blocked stress (TMT)-induced alcohol relapse in mice with and without a history of chronic stress exposure. Proposed studies in this application are designed to build on and expand these compelling and supportive pilot findings. The overall objective of this proposal is to optimize and further characterize our model of PTSD that captures many key clinical features of the disorder, link consequences of the model to alcohol self- administration and relapse behavior, and examine the role of the neurohormone oxytocin in this mouse model of PTSD-AUD comorbidity. Specifically, after more fully characterizing the chronic predator odor (TMT) model, we will examine whether CES similarly sensitizes mice to stress-induced alcohol relapse and then use these procedures in combination to examine whether CES experience further augments the ability of chronic TMT exposure to subsequently sensitize mice to acute stress challenge provoking alcohol relapse-like behavior. This unique mouse model of PTSD-AUD will then be used to probe involvement of the oxytocin system, with studies also examining the capacity of exogenous OT treatment to block and/or prevent sensitized stress-induced alcohol relapse in the CES-TMT model. The overall goal is to establish and utilize a clinically relevant mouse model of PTSD-AUD that will advance our understanding of these co- occurring disorders and facilitate development of more effective treatments for PTSD-AUD comorbidity.