Pathological AMPA receptor adaptations governing dependence-escalated alcohol self-administration

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Project Summary Alcohol dependence and multiple withdrawal experiences are related to increased severity of alcohol use disorder (AUD), craving, and resistance to treatment. Alcohol abuse gains control over behavior, in part, through pathological adaptations of glutamatergic AMPA receptor (AMPAR) mechanisms that regulate synaptic and behavioral plasticity in brain reward pathways. The unique auxiliary protein, transmembrane AMPAR regulatory protein (TARP) γ-8, has been shown to regulate AMPAR trafficking, activity, and CaMKII-dependent plasticity, making it critical for AMPAR mediated neural transmission. An important feature of TARP γ-8 is its highly restricted expression limited to corticolimbic regions known to regulate glutamatergic response to alcohol including the medial prefrontal cortex (mPFC), basolateral amygdala (BLA), and the hippocampus, while noticeably absent from the nucleus accumbens (NAc). Evidence indicates chronic alcohol increases glutamate levels, which in turn promotes the influx of calcium, and initiating a cascade where CaMKII phosphorylates AMPARs to increase and sustain AMPAR activity. Since AMPAR activity is required for the development of new behavior (e.g., learning) and retention of actions (e.g., memory), this fundamental neural process may underlie the development, maintenance, and critically, dependence-escalated self-administration of alcohol. Therefore, this K99/R00 proposal will determine if TARP γ-8 regulates AMPAR mediated transmission in key brain regions during dependence-escalated alcohol self-administration. Aim 1 (K99 phase) of the proposal will investigate the role of TARP γ-8 dependent excitatory Ca2+ signaling in reward-related brain regions during alcohol self- administration in the mPFC, BLA, NAc, and vHPC using a highly novel multi-spectral, four-channel fiber photometry platform. Aim 2 (K99 phase) will examine TARP γ-8 as a mechanism of CIE vapor dependence- induced escalation of alcohol self-administration and the consequential co-localization of TARP γ-8 and AMPAR using confocal microscopy. Aim 3 (R00 phase) combines these techniques to evaluate Ca2+ signaling in key- reward brain regions during dependence-escalated alcohol self-administration. These findings are then extended by taking a circuit-based approach using a selective pharmacological manipulation in combination with fiber- photometry to evaluate site-specific TARP γ-8 bound AMPAR inhibition on “bottom-up” (BLA to NAc) and “top- down” (mPFC to NAc) Ca2+ signaling. This work moves the field forward by providing fundamental mechanistic insights into TARP γ-8 dependence-escalated alcohol self-administration which has high translational value for understanding and treating AUD and has the potential to inform development of new pharmacotherapeutic strategies that target AMPAR function in a highly-selective brain region specific manner.