Faccidomo Sara, Hoffman Jessica L, Lee Julie, Whindleton Ciarra M, Kim Michelle, Taylor Seth M, Kim April, Richter Caroline, Seiters Hanna L, Bryant Jacob M, Chang Ashley, Smith Evan N, Agoglia Abigail E, Tomita Susumu, Herman Melissa A, Hodge Clyde W
bioRxiv. 2025 Apr 1:2025.03.27.645788. doi: 10.1101/2025.03.27.645788.
Behavioral pathologies that characterize alcohol use disorder (AUD) are driven by the powerful reinforcing, or rewarding, properties of the drug. We have shown that glutamate AMPA receptor (AMPAR) activity is both necessary and sufficient for alcohol (ethanol) reinforcement. Transmembrane AMPAR regulatory protein (TARP) γ-8 is an essential auxiliary protein that regulates AMPAR expression and activity; however, the role of TARP ɣ-8 in AUD or other forms of addiction remains largely unexplored.
This study investigated the mechanistic role of TARP γ-8 in operant ethanol self-administration (model of primary reinforcement) and cue-induced reinstatement of ethanol-seeking behavior (model of conditioned reinforcement) using TARP ɣ-8 heterozygous null (+/-) mice. To determine if TARP ɣ-8 signaling is targeted by ethanol use, we evaluated protein expression of TARP γ-8, GluA1, CaMKII, and PSD-95 following ethanol self-administration.
A battery of tests evaluating food and water intake, taste reactivity, anxiety-like behavior, and object recognition memory showed no fundamental behavioral deficits in TARP γ-8 (+/-) mice, and no differences in response to acute ethanol or home-cage drinking as compared to wild-types. However, TARP γ-8 (+/-) mice exhibited significantly reduced acquisition and escalation of operant ethanol self-administration and reduced cue-induced reinstatement of ethanol-seeking behavior, with no differences in parallel sucrose-only controls. In wild-type mice, ethanol self-administration increased TARP γ-8 expression in the amygdala, nucleus accumbens, and hippocampus, and increased GluA1 expression in the amygdala and prefrontal cortex, compared to sucrose controls.
These findings highlight the specificity of TARP ɣ-8 regulation of ethanol reinforcement mechanisms and identify this crucial AMPAR auxiliary protein as a target of ethanol in reward-related brain regions, highlighting its potential for development of novel pharmacotherapies for AUD.
酒精使用障碍（AUD）所具有的行为病理学特征是由该药物强大的强化或奖赏特性驱动的。我们已经表明，谷氨酸α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体（AMPAR）活性对于酒精（乙醇）强化作用而言既是必要的也是充分的。跨膜AMPAR调节蛋白（TARP）γ-8是一种调节AMPAR表达和活性的重要辅助蛋白；然而，TARPγ-8在AUD或其他成瘾形式中的作用在很大程度上仍未得到探索。
本研究使用TARPγ-8杂合缺失（+/-）小鼠，研究了TARPγ-8在操作性乙醇自我给药（初级强化模型）和线索诱导的乙醇寻求行为恢复（条件性强化模型）中的机制作用。为了确定乙醇使用是否靶向TARPγ-8信号传导，我们评估了乙醇自我给药后TARPγ-8、GluA1、CaMKII和PSD-95的蛋白表达。
一系列评估食物和水摄入量、味觉反应性、焦虑样行为和物体识别记忆的测试表明，TARPγ-8（+/-）小鼠没有基本的行为缺陷，并且与野生型相比，对急性乙醇或笼内饮水的反应没有差异。然而，TARPγ-8（+/-）小鼠表现出操作性乙醇自我给药的习得和升级显著减少，以及线索诱导的乙醇寻求行为恢复减少，而在平行的仅蔗糖对照中没有差异。在野生型小鼠中，与蔗糖对照相比，乙醇自我给药增加了杏仁核、伏隔核和海马体中TARPγ-8的表达，并增加了杏仁核和前额叶皮质中GluA1的表达。
这些发现突出了TARPγ-8对乙醇强化机制调节的特异性，并确定这种关键AMPAR辅助蛋白是奖励相关脑区中乙醇的作用靶点，突出了其作为AUD新型药物疗法开发潜力。
