Role of Rostromedial Tegmental Nucleus in alcohol addiction

描述(由申请人提供)：乙醇成瘾特性的神经生物学机制仍不清楚。人们普遍认为，乙醇的成瘾特性与其增加大脑腹侧被盖区(VTA)多巴胺能神经元的活动有关。这些神经元处于突触输入的强大控制之下。因此，多巴胺能神经元的突触调节是导致酒精成瘾的奖赏机制的关键初始步骤。多巴胺能神经元的大部分传入是GABA能的，通常是抑制性的。一些滥用药物，如阿片类药物，通过抑制GABA能传递来刺激VTA-多巴胺能神经元--即通过去抑制。新的证据表明，被盖旋转内侧核是多巴胺能神经元的主要GABA能传入，是μ阿片受体依赖性调节多巴胺能神经元的关键结构，具有密集的μ阿片受体免疫反应性。然而，与饮酒行为有关的RMTg输入与多巴胺能神经元之间的功能机制仍然不清楚。我们的长期目标是了解酒精成瘾的神经生物学机制。本应用的目的是通过确定RMTg在乙醇诱导的VTA多巴胺能神经元激活中的作用，以及确定RMTg神经元活动对酒精摄入的影响，来确定RMTg在酒精饮酒行为中的作用。我们提出的实验将专门验证这一中心假设，即RMTg投射到VTA多巴胺能细胞通过强烈调节酒精诱导的VTA-多巴胺能神经元活性的增强，在调控酒精饮酒行为中发挥关键作用。这一核心假设将在两个独立但综合的目标中得到检验。目的1将结合体外电生理学、轨迹示踪实验、靶向神经元激活/失活、分子遗传学和光遗传学技术，从功能上剖析急性乙醇对多巴胺能神经元的作用。目的2将确定改变RMTg活性对乙醇摄入量的影响。为了验证RMTg在饮酒中起关键作用的假设，我们将通过RMTg内注入相关药理学药物来操纵RMTg的功能，然后使用间歇性的2瓶选择范式来研究酒精摄入量的相应变化。这些研究意义重大，因为它们将促进我们对决定过量饮酒的神经回路的了解。这些研究具有创新性，因为它们将表征之前未被充分研究的酒精对下丘脑室旁核神经元的影响，以及随后对下丘脑室旁核-多巴胺能神经元的间接影响，以及μ-阿片受体在下丘脑室旁核在饮酒行为中的作用。该项目的结果将提供关于酒精成瘾特性的新机制的有价值的信息，并将为改进酒精中毒治疗的开发确定新的细胞靶点。

DESCRIPTION (provided by applicant): The neurobiological mechanisms underlying the addictive property of ethanol remain obscure. It is generally accepted that the addictive property of ethanol is associated with its ability to increase the activity of dopaminergic neurons in the ventral tegmental area (VTA) in the brain. These neurons are under the powerful control of synaptic inputs. Thus, the synaptic regulation of dopaminergic neurons is a key initial step in reward mechanisms leading to alcohol addiction. The majority of the afferents to dopaminergic neurons are GABAergic and usually inhibitory. Some drugs of abuse, such as opioids, stimulate VTA-dopaminergic neurons through suppression of GABAergic transmission - that is by disinhibition. Emerging evidence indicates that the rostromedial tegmental nucleus (RMTg), a newly defined structure with dense μ-opioid receptor immunoreactivity, is a major GABAergic afferent to dopaminergic neurons, and a key structure in μ-opioid receptor-dependent regulation of dopaminergic neurons. However, the functional mechanisms connecting the RMTg inputs to the dopaminergic neurons with alcohol drinking behavior remain obscure. Our long term goal is to understand the neurobiological mechanisms underlying alcohol addiction. The objective in this application is to define RMTg's role in ethanol drinking behavior by identifying its contribution to ethanol-induced activation of VTA dopaminergic neurons and determining the influence of RMTg neuronal activity on ethanol intake. Our proposed experiments will specifically test the central hypothesis that the RMTg projection to VTA dopaminergic cells plays a key role in the control of regulating ethanol drinking behavior by strongly regulating ethanol-induced enhancement of VTA-dopaminergic neuron activity. This central hypothesis will be tested in two separate but integrated Aims. Aim 1 will combine ex vivo electrophysiology, tract tracing experiments, targeted neuronal activation/inactivation, molecular genetics and optogenetic techniques to functionally dissect a neuronal circuit important for acute ethanol's action on dopaminergic neurons. Aim 2 will determine the effect of altering RMTg activity on ethanol intake. To test the hypothesis that the RMTg plays a key role in ethanol drinking, we will manipulate RMTg function by intra-RMTg infusion of relevant pharmacological agents and then study consequent changes in ethanol intake, using the intermittent 2-bottle choice paradigm. The studies are significant because they will advance our knowledge of the neural circuitries that determine excessive alcohol consumption. The proposed studies are innovative, because they will characterize a previously understudied effect of ethanol on the RMTg neurons, and its subsequent indirect effect on VTA-dopaminergic neurons, as well as the role of μ-opioid receptors in the RMTg in drinking behavior. The results of this project will provide valuable information on novel mechanisms underlying the addictive properties of alcohol and should identify novel cellular targets for the development of improved treatment of alcoholism.