PROJECT SUMMARY This NIH Small Research Grant Program (Parent R03) application proposes support for early stage investigator Terril Verplaetse, Ph.D., to establish a new research program in the area of neuroinflammation and alcohol research. Neuroimmune function is a key system linked to negative reinforcement drinking and to the development of alcohol use disorder (AUD). Stress and chronic alcohol consumption have been found to increase microglial activity, a marker of neuroinflammation. However, the role of neuroinflammation on alcohol use behavior is less clear. Endotoxin, also called lipopolysaccharide (LPS), is well-known to induce neuroinflammation and acute stress. In preclinical studies, LPS increases voluntary ethanol intake. {{{To our knowledge, a provocation study to examine neuroinflammation-induced drinking has not been developed in humans with AUD.}}}. Further, rates of AUD have increased in women by 84% over the past ten years relative to a 35% increase in men. Stress and greater neuroimmune response are associated with alcohol use for both women and men but play an especially critical role in women. Thus, this application will generate data to calculate effect sizes for the interaction between sex and endotoxin (vs. placebo) administration on drinking behavior and potential mechanisms underlying endotoxin effects on drinking in women vs. men. The goal of this proposed research is to examine the role of neuroinflammation on acute drinking in women and men and to investigate sex differences in potential mechanisms underlying the role of neuroinflammation on alcohol self- administration. The study population will be individuals meeting DSM-5 criteria for AUD. This project features a well-validated human laboratory paradigm that models two critical features of drinking behavior; the ability to resist drinking (i.e., reducing time to initiate drinking) and subsequent ad-libitum drinking (i.e., milliliters of alcohol consumed). To determine whether endotoxin (vs. placebo) increases our primary outcomes of time to initiate drinking and amount of alcohol consumed in women and men, individuals will complete a single laboratory session in which LPS (vs. placebo; {{{double-blinded}}}) is administered prior to a 2-hour alcohol self-administration session (Specific Aim 1). We will also evaluate the safety of endotoxin in combination with alcohol in individuals with AUD (Specific Aim 2). Additional analyses will examine potential sex differences in mechanisms underlying endotoxin (vs. placebo) effects on drinking behavior (e.g., peripheral cytokines, craving, subjective intoxication, mood, stress, heart rate, blood pressure, cortisol, ACTH, {{{and sex hormones}}}) over the course of the 2-hour alcohol self-administration session (Specific Aim 3). Taken together, this proposal will provide valuable data for evaluating the role of neuroinflammation on alcohol- motivated behavior and will have abundant applications to inform novel pharmacotherapeu...