Alcohol use disorder (AUD) is highly prevalent among U.S. military veterans. Excessive alcohol consumption, defined as the acquisition of a blood alcohol concentration (BAC) ≥ 0.08 g/dl (binging) or ≥ 15 drinks/week for men, is an important risk factor for many serious medical and psychiatric conditions, including AUD. The medial prefrontal cortex (mPFC) is important for integrating various internal and external states in order to determine approach/avoidant behavior to rewarding or aversive stimuli. Prior studies demonstrated that Poly- ADP ribose Polymerase (PARP), through its ability to regulate synaptic plasticity gene expression, promotes cocaine addictive behaviors. Whether PARP enzymatic activity plays a similar role in the addictive properties of ethanol (EtOH) has yet to be studied. The hypothesis of this grant proposal is that EtOH increases PARP activity causing reduced expression of certain neuronal synaptic plasticity genes in excitatory mPFC neurons ultimately increasing alcohol drinking behavior. EtOH increases PARP enzymatic activity in cell culture, adult binging animals, and during fetal development. PARP can silence gene expression by catalyzing reactions adding PAR groups (PARylation) to downstream gene regulatory proteins, including the transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) and KDM4D, a demethylase of the transcriptionally repressive dimethylated lysine 9 of histone 3 (H3K9me2). Examples of genes implicated in AUD that are well- established to be regulated by H3K9me2 are Brain-derived Neurotrophic Factor (Bdnf) and Pparγ. BDNF and PPARγ are expressed by excitatory neurons in the cortex, where both have roles in synaptic plasticity and neuronal survival. Therefore, an alcohol induced suppression of BDNF and PPARγ expression would be expected to alter mPFC excitatory outputs, promoting continued alcohol drinking behavior. This is supported by reports indicating higher BDNF expression and PPARγ agonists reduce alcohol consumption. We reported that PARP activity is in part responsible for EtOH-induced decreases in Bdnf IV and IXa mRNA expression in primary cortical neuron cultures. We found several lines of evidence indicating that reduced PPARγ promoter binding may serve as an intermediary step between increased PARP activity and decreased Bdnf expression. We now propose to examine these same pathways in vivo. Our preliminary data indicate that mice that voluntarily consumed EtOH in the binge-like drinking-in-the-dark (DID) paradigm had increased PARP mRNA expression and enzymatic activity in the PFC. DID consumed EtOH reduced BDNF and PPARγ expression, effects that were reversed by PARP inhibitor treatment. DID EtOH consumption decreased PPARγ DNA binding ability generally and specifically at the Bdnf IXa promoter. Also, DID consumed EtOH increased global levels of H3K9me2, and PARP inhibition decreased H3K9me2 at Pparγ and Bdnf IXa gene promoters. Finally, we found that PARP inhibition reduc...