Drug targeting the dynamics of opioid systems in alcohol dependence

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PROJECT SUMMARY Alcohol use disorder (AUD) is a serious condition with severe medical and societal consequences.There has been little progress in medical treatment over the past decades. We are taking a translational approach and have established an animal model, where alcohol-dependent rats in various stages of abstinence are subjects of investigation. The neuronal target is the opioid systems and the opponent hypothesis. We propose that the initial euphoric effects are channeled through the enkephalin/mu-opioid receptor (MOP) and the later developing negative reinforcement (craving) is related to activity at the dynorphin/kappa-opioid receptor (KOP). In fact, the MOP antagonist, naltrexone is a FDA-approved agent with indication to reduce relapse. KOP antagonists are entering clinical trials in different neuropsychiatric conditions. We have chosen CERC-501 as index drug, being reversible and apparently well tolerated in clinical examination. After behavioral recordings, brain specimens will be dissected and form a “brain bank” for further analysis. A focus of interest is the central nucleus of the amygdala (CeA), and the circuitry presenting MOP and/or KOP. Selected specimens will undergo superresolution microscopy (quantitative Single Molecule Localization Microscopy, qSMLM). A pilot study showed that already an acute dose of EtOH disrupts localization of MOP and KOP, an effect blocked by naltrexone. How EtOH affects receptor mobility in the plasma membrane, receptor clustering (homo- and hetero-dimers) and association with protein- and lipid-rich membrane domains will be studied by fluorescence correlation spectroscopy (FCS). As with qSMLM resolution is achieved at the single-molecule level. Both technologies will be used to study co- localization of receptors with proteins of relevance for the signaling cascade. We hypothesize that EtOH perturbs the dynamic selforganization of signaling domains harboring MOPs and KOPs, that distinct alterations in mechanisms controlling MOP vs KOP organization develop during chronic EtOH exposure. With OP antagonists innate MOP and KOP signaling complexes are stabilized at the nanoscale level. Focused studies of these mechanisms will provide critical new insight into molecular mechanisms through which EtOH-induced receptor disruptions may be prevented or reversed. The commensurate importance of the two opioid systems may vary between individuals and influence the choice of personalized therapy with OP antagonists. Studies will include the N40D MOP genotype known to affect the behavioral phenotype and sensitivity to naltrexone.