Adolescent Binge Drinking Increases Adult Alcohol Intake: Glutamate Mechanisms

描述(由申请人提供)： 酗酒，定义为使血液酒精水平达到80毫克或以上的饮酒，在青少年和年轻人中一直在增加，这种先前的经历是未来生活中酒精依赖的强烈预测因素。证据还表明，酗酒在军队中是一个长期存在的问题，在进入军队的年轻人中很普遍，酒精使用障碍或酗酒与退伍军人的健康状况受损和慢性健康问题有关。然而，尽管酗酒和酒精使用障碍会导致美国退伍军人的健康问题，但酒精滥用背后的生理机制仍然知之甚少。这在一定程度上是由于酒精在多个受体和离子通道上的作用。与目前的提议相关的是，越来越多的证据表明，谷氨酸能神经传递功效的活动依赖变化是成瘾大脑中的一个主要潜在事件。这些神经适应机制可能反映了异常大脑可塑性的表现，已有研究表明，青春期大脑可塑性的增强与成瘾易感性的增强在时间上相关。考虑到这一点，本提案基于强有力的初步数据，该数据表明，酗酒会导致谷氨酸能系统发生变化，该系统可以与压力相互作用，从而增强随后的酒精饮酒行为，而且青春期小鼠可能比成年小鼠更容易受到这些扰动的影响。我们已经建立了一个酗酒模型(预定的高酒精消耗量，SHAC)，并发现青春期的酗酒经历显著增加了成年小鼠的酒精摄入量，在暴露于约束压力后进一步增加。重要的是，青少年比成年人对酗酒对后续摄入量的影响更敏感。代谢性受体5亚型(MGluR5)拮抗剂可减少SHAC过程中的酗酒，并上调伏隔核(NAC)mGluR5-Hmer 2-磷脂酰肌醇3-激酶(PI3K)信号。与细胞外谷氨酸水平(通过微透析)和神经末梢谷氨酸免疫标记之间的反向关系一致，反复狂饮显著增加细胞外谷氨酸水平，并减少神经末梢内的谷氨酸免疫标记，使不对称(兴奋性)突触接触。基于这一证据，拟议研究的目标是检验一种假设，即酗酒后谷氨酸神经可塑性的适应使青春期小鼠在成年期增加酒精摄入量的易感性。第二个假设是，压力会产生额外的适应能力，使人更容易受到酒精摄入量增加的影响。拟议的研究将在雄性和雌性青春期和成年C57BL/6小鼠身上进行，因为我们预测在酗酒和暴露于压力后发生的谷氨酸能神经适应会有性别(女性和男性)和年龄(青春期和成人)的差异。具体的目标将使用多学科方法来确定身体或心理应激源是否会对随后的酒精摄入产生相加效应(目标1)，以及NAC内谷氨酸免疫标记和树突大小的变化(目标2)以及谷氨酸能基因和信号通路的表达变化(目标3)是否对应于压力和狂饮后酒精摄入量的增加。这些研究将确定伏隔谷氨酸的变化是否是一个重要的神经生物学机制，使人们在酗酒和暴露于压力后增加对酒精依赖的易感性。这些信息可以指导酒精使用障碍或酗酒的药物治疗策略，这是我们退伍军人治疗的一个重要领域。

DESCRIPTION (provided by applicant): Binge drinking, defined as drinking that brings blood alcohol levels to 80 mg% or above, has been increasing in adolescents and young adults, and this prior experience is a strong predictor of alcoholic dependence later in life. Evidence also indicates that binge drinking is a persistent problem in the military and is prevalent among young adults entering the military, and that alcohol use disorder or binge drinking are associated with impaired health status and chronic health problems in veterans. However, while alcoholism and alcohol use disorder contribute to health problems in the US veteran population, the physiological mechanisms underlying alcohol abuse remain poorly understood. This is due in part, to alcohol's actions at multiple receptors and ion channels. Relevant to the present proposal, increasing evidence implicates activity dependent changes in the efficacy of glutamatergic neurotransmission as a major underlying event in the addicted brain. These neuroadaptive mechanisms may reflect manifestations of aberrant brain plasticity, and it has been suggested that the enhanced plasticity of the adolescent brain temporally correlates with enhanced vulnerability to addiction. With this in mind, the present proposal is based on strong preliminary data suggesting that binge drinking produces alterations in the glutamatergic system that can interact with stress to augment subsequent ethanol drinking behavior, and that adolescent mice may be more susceptible than adult mice to the impact of these perturbations. We have developed a model of binge drinking (Scheduled High Alcohol Consumption, SHAC) and found that binge drinking experience in adolescent mice significantly increased ethanol intake during adulthood, with further increases following exposure to restraint stress. Importantly, adolescents were more sensitive than adults to the impact of binge drinking on subsequent intake. Binge drinking with the SHAC procedure was decreased by a metabotropic receptor subtype 5 (mGluR5) antagonist, and it upregulated nucleus accumbens (NAc) mGluR5-Homer2-phosphatidylinositol 3-kinase (PI3K) signaling. Consistent with the inverse relationship between extracellular glutamate levels (via microdialysis) and nerve terminal glutamate immunolabelling, repeated bouts of binge drinking significantly increased extracellular glutamate levels and decreased glutamate immunolabelling within nerve terminals making asymmetrical (excitatory) synaptic contacts. Based on this evidence, the goal of the proposed studies is to test the hypothesis that adaptations in glutamate neuroplasticity following binge drinking confer susceptibility for enhanced alcohol intake in adolescent mice during adulthood. A secondary hypothesis is that stress produces additional adaptations that bestow further vulnerability for increased alcohol consumption. The proposed studies will be conducted in male and female adolescent and adult C57BL/6 mice, since we predict that there will be sex (female > male) and age (adolescent > adult) differences in the glutamatergic neuroadaptations that occur following binge drinking and exposure to stress. The specific aims will use a multidisciplinary approach to determine whether physical or psychological stressors will have an additive effect with binge drinking on subsequent ethanol intake (Aim 1), and whether alterations in glutamate immunolabelling and dendritic spine size (Aim 2) as well as alterations in the expression of glutamatergic genes and signaling pathways (Aim 3) within the NAc correspond to the escalation in ethanol intake following stress and binge drinking. These studies will determine whether alterations in accumbal glutamate are an important neurobiological mechanism that confers increased susceptibility for alcohol dependence following binge drinking and exposure to stress. This information can guide pharmacological treatment strategies for alcohol use disorder or binge drinking, an important area of focus in the treatment of our veterans.