Biochemical Studies Underlying Acute Ethanol's Antidepressant-like effects during Withdrawal in a Preclinical Model of Ethanol Dependence

PROJECT SUMMARY Major depressive disorder (MDD) and alcohol use disorder (AUD) are comorbid. Acute alcohol decreases both anxiety- and depressive-like behaviors. Chronic alcohol exposure increases both of these negative emotion- like behaviors. In fact, decades of epidemiological data suggest that individuals use alcohol to alleviate a negative affective state. Whether the negative emotional state is due to MDD or repeated alcohol exposure (AUD), researchers are now beginning to examine how mechanisms that are initially positive and rewarding shift toward negative affect/anhedonia during withdrawal. For example, much is known about the neural circuitry and neurotransmitter/peptide systems underlying acute and chronic effects of alcohol on anxiety-like behaviors. Surprisingly, much less attention has been directed at the negative affective (anhedonia) component. Our preclinical work suggests that acute ethanol treatment produces an antidepressant-like effect and hijacks the same biochemical pathway as NMDAR antagonists. Pivotal to ethanol and NMDAR antagonists’ antidepressant efficacy is the dynamic expression of the RNA-binding protein Fragile X Mental Retardation Protein (FMRP). Reduction in FMRP expression allows for the upregulation of transsynaptic proteins that promote new synapse formation and antidepressant-like effects. Consistent with a shift from positive to negative emotion-like behaviors, FMRP is upregulated during withdrawal in ethanol-dependent animals. Using molecular, biochemical, and electrophysiological techniques, combined with a novel synapse detection assay that we developed in our laboratory (DetectSyn), and the expertise of our collaborators in the Weiner laboratory in preclinical models of alcohol dependence, we will determine in Specific Aim 1 if acute ethanol regulates the binding of FMRP to transsynaptic mRNAs, regulates the synaptic protein synthesis of these target mRNAs, and promotes new synapse formation. Moreover, in Specific Aim 2 we will determine if the FMRP-regulated antidepressant signaling pathway is muted or suppressed during the WD/negative affect state, and if acute ethanol treatment can reverse the biochemical and behavioral depressive phenotypes. Furthermore, we will isolate and sequence FMRP target mRNAs that are repressed during WD but released due to treatment with acute ethanol during WD. Using a computational/genomic approach such as the Library of Integrated Network-Based Cellular Signatures – a method that has shown promise in AUD research – these data will facilitate future studies using these targets to predict effective, repurposed FDA-approved drugs to treat AUD and MDD. These studies will lay the foundation for future pharmacological intervention to treat negative affect during WD in alcohol-dependent individuals with comorbid MDD.