Stress and Ethanol Dependence: SK Channels and Glutamate

描述(由申请人提供)：大量饮酒和反复戒酒与下丘脑-垂体-肾上腺(HPA)轴的复发和平衡适应增加有关。过量饮酒还与皮质-边缘-HPA功能紊乱有关，这可能导致酒精依赖和高复发率。我们的初步证据表明，酒精依赖小鼠自愿饮酒的一个关键调节因素是小电导钙激活钾(SK)通道。内侧前额叶皮质(MPFC)和伏隔核(NAC)中的SK通道调节依赖NMDA受体的钙内流、内源性兴奋性和基础放电频率。我们的初步研究结果表明，慢性间歇性乙醇(CIE)暴露或长期应激后，C57BL/6J小鼠mPFC和NAC中SK通道的表达显著减少。此外，微量注射研究表明，阻断NAC中SK通道的活动可以增加对照组小鼠的自愿饮酒，但不会增加酒精依赖小鼠的自愿饮酒。这些数据表明，在CIE后观察到的SK通道的下调与CIE暴露小鼠的饮酒升级密切相关。因此，这一建议的主要假设是，CIE通过增加NMDA受体和减少控制饮酒的关键大脑区域的SK通道活动来增加谷氨酸能突触的兴奋。这些研究将检验以下假设：1)慢性酒精暴露和应激改变谷氨酸能突触；2)转基因小鼠不同的饮酒模式与SK通道表达的变化有关；3)mPFC和NAC中的SK通道调节CIE暴露小鼠的饮酒升级。我们希望从这些研究中收集的数据将促进我们对涉及酒精寻求行为的关键脑区突触可塑性的理解，并将验证SK通道是治疗酒精依赖的重要新靶点的假设。

DESCRIPTION (provided by applicant): Heavy alcohol drinking and repeated withdrawals are associated with increased relapse and allostatic adaptations in the hypothalamic-pituitary-adrenal (HPA) axis. Excessive alcohol intake is also associated with perturbations in cortico-limbic-HPA function that may contribute to alcohol dependence and high rates of relapse. Our preliminary evidence suggests that a critical modulator of high rates of voluntary drinking in alcohol-dependent mice is the small-conductance calcium-activated potassium (SK) channels. SK channels in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc) regulate NMDA receptor-dependent calcium influx, intrinsic excitability, and basal firing rates. Results from our preliminary studies demonstrate that SK channel expression is significantly reduced in mPFC and NAc in C57BL/6J mice following chronic intermittent ethanol (CIE) exposure or prolonged stress. Moreover, microinjection studies show that blocking SK channel activity in NAc enhances voluntary consumption in control, but not alcohol-dependent mice. These data suggest that the down-regulation of SK channels observed following CIE is critically involved in the escalation of drinking in CIE exposed mice. Thus, the overarching hypothesis of this proposal is that CIE increases the excitation at glutamatergic synapses through a combination of increased NMDA receptors and a decrease in SK channel activity in key brain regions that control drinking. These studies will test the hypotheses that: 1) chronic ethanol exposure and stress alter glutamatergic synapses, 2) divergent drinking patterns in genetically modified mice are linked to alterations in SK channel expression, and 3) SK channels in mPFC and NAc regulate escalation of drinking in CIE exposed mice. We expect that data collected from these studies will advance our understanding of synaptic plasticity in key brain regions involved in alcohol seeking behaviors and will validate the hypothesis that SK channels are an important new therapeutic target for the treatment of alcohol dependence.