Role of Rostromedial Tegmental Nucleus in alcohol addiction

描述（由申请人提供）：乙醇成瘾特性背后的神经生物学机制仍然不清楚。人们普遍认为，乙醇的成瘾性与其能够增加大脑腹侧被盖区（VTA）多巴胺能神经元的活性有关。这些神经元受到突触输入的强大控制。因此，多巴胺能神经元的突触调节是导致酒精成瘾的奖励机制的关键初始步骤。大多数多巴胺能神经元的传入是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。新发现的证据表明，RMTg （rostromedial tetemental nucleus）是多巴胺能神经元gaba能的主要传入结构，是多巴胺能神经元依赖μ-阿片受体调控的关键结构，是一种具有较强μ-阿片受体免疫反应性的新结构。然而，将RMTg输入与多巴胺能神经元与饮酒行为联系起来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。本应用程序的目的是通过确定RMTg对乙醇诱导的VTA多巴胺能神经元激活的贡献，以及确定RMTg神经元活动对乙醇摄入的影响，来确定RMTg在乙醇饮酒行为中的作用。我们提出的实验将专门验证RMTg投射到VTA多巴胺能细胞的中心假设，即通过强烈调节乙醇诱导的VTA多巴胺能神经元活动的增强，在调节乙醇饮酒行为的控制中起关键作用。这一中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、通道追踪实验、靶向神经元激活/失活、分子遗传学和光遗传学技术，对急性乙醇对多巴胺能神经元的作用至关重要的神经元回路进行功能解剖。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在乙醇饮用中发挥关键作用的假设，我们将通过RMTg内输注相关药物来操纵RMTg功能，然后使用间歇性两瓶选择范式研究乙醇摄入量的随之变化。这些研究意义重大，因为它们将推进我们对决定过度饮酒的神经回路的了解。这些研究具有创新性，因为它们将描述先前未被充分研究的乙醇对RMTg神经元的影响，及其随后对vta -多巴胺能神经元的间接影响，以及μ-阿片受体在RMTg中饮酒行为的作用。该项目的结果将为酒精成瘾特性的新机制提供有价值的信息，并为改进酒精中毒治疗的发展确定新的细胞靶点。

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.