Bowles Center for Alcohol Studies, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Department of Psychiatry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Addict Biol. 2021 Sep;26(5):e13049. doi: 10.1111/adb.13049. Epub 2021 May 5.
Addiction is viewed as maladaptive glutamate-mediated neuroplasticity that is regulated, in part, by calcium-permeable AMPA receptor (CP-AMPAR) activity. However, the contribution of CP-AMPARs to alcohol-seeking behavior remains to be elucidated. We evaluated CP-AMPAR activity in the basolateral amygdala (BLA) as a potential target of alcohol that also regulates alcohol self-administration in C57BL/6J mice. Operant self-administration of sweetened alcohol increased spontaneous EPSC frequency in BLA neurons that project to the nucleus accumbens as compared with behavior-matched sucrose controls indicating an alcohol-specific upregulation of synaptic activity. Bath application of the CP-AMPAR antagonist NASPM decreased evoked EPSC amplitude only in alcohol self-administering mice indicating alcohol-induced synaptic insertion of CP-AMPARs in BLA projection neurons. Moreover, NASPM infusion in the BLA dose-dependently decreased the rate of operant alcohol self-administration providing direct evidence for CP-AMPAR regulation of alcohol reinforcement. As most CP-AMPARs are GluA1-containing, we asked if alcohol alters the activation state of GluA1-containing AMPARs. Immunocytochemistry results showed elevated GluA1-S831 phosphorylation in the BLA of alcohol as compared with sucrose mice. To investigate mechanistic regulation of alcohol self-administration by GluA1-containing AMPARs, we evaluated the necessity of GluA1 trafficking using a TET-ON AAV encoding a dominant-negative GluA1 c-terminus (GluA1ct) that blocks activity-dependent synaptic delivery of native GluA1-containing AMPARs. GluA1ct expression in the BLA reduced alcohol self-administration with no effect on sucrose controls. These results show that CP-AMPAR activity and GluA1 trafficking in the BLA mechanistically regulate the reinforcing effects of sweetened alcohol. Pharmacotherapeutic targeting these mechanisms of maladaptive neuroplasticity may aid medical management of alcohol use disorder.
成瘾被视为适应不良的谷氨酸能神经可塑性，部分受钙通透性 AMPA 受体 (CP-AMPAR) 活性调节。然而，CP-AMPAR 对酒精觅药行为的贡献仍有待阐明。我们评估了外侧杏仁核 (BLA) 中的 CP-AMPAR 活性，作为酒精的潜在靶点，该靶点也调节 C57BL/6J 小鼠的酒精自我给药。与行为匹配的蔗糖对照相比，加糖酒精的操作性自我给药增加了投射到伏隔核的 BLA 神经元的自发 EPSC 频率，表明突触活性的酒精特异性上调。CP-AMPAR 拮抗剂 NASPM 的浴应用仅在酒精自我给药的小鼠中降低了诱发 EPSC 幅度，表明 CP-AMPAR 在 BLA 投射神经元中诱导了酒精诱导的突触插入。此外，BLA 中的 NASPM 输注剂量依赖性地降低了操作性酒精自我给药的速度，为 CP-AMPAR 调节酒精强化提供了直接证据。由于大多数 CP-AMPAR 都含有 GluA1，我们想知道酒精是否改变了含有 GluA1 的 AMPAR 的激活状态。免疫细胞化学结果显示，与蔗糖相比，酒精组 BLA 中的 GluA1-S831 磷酸化水平升高。为了研究含有 GluA1 的 AMPAR 对酒精自我给药的机械调节，我们使用编码显性负性 GluA1 C 端 (GluA1ct) 的 TET-ON AAV 评估了 GluA1 易位的必要性，该 C 端可阻止天然 GluA1 含有 AMPAR 的活性依赖性突触传递。BLA 中的 GluA1ct 表达减少了酒精自我给药，对蔗糖对照无影响。这些结果表明，BLA 中的 CP-AMPAR 活性和 GluA1 易位在机制上调节了加糖酒精的强化作用。针对这些适应性神经可塑性机制的药物治疗可能有助于酒精使用障碍的医学管理。
