Presynaptic versus postsynaptic functions of dopamine D2 receptors in the respons

描述（由申请人提供）：成瘾是一个主要的健康和社会问题。多巴胺能系统受到药物滥用的高度诱导，因为多巴胺释放的增加是药物摄入效果的标志。多巴胺D2受体（D2R）是多巴胺能系统的关键组成部分。事实上，它除了在中枢神经系统中广泛而丰富的突触后分布外，还作为自身受体控制多巴胺的合成和释放。D2Rs也调节其他神经递质的释放从突触后神经元作为突触前异受体。D2Rs在体内由两个异构体D2L和D2S组成，它们是由同一基因通过选择性剪接产生的。本研究的目的是证明多巴胺D2受体介导的突触前自身受体/异突触控制在药物滥用的行为和细胞反应中发挥主要作用。这一假设是基于我们实验室进行的初步研究，该研究表明小鼠D2受体信号（D2R-/-）的缺失会强烈改变对精神兴奋剂和其他滥用药物的反应。相反，在D2L-/-不表达具有突触后功能的受体的D2L异构体（即对激动剂/拮抗剂的行为和细胞药理反应），但保持突触前/异突触受体功能的表达（即控制DA释放，可卡因诱导纹状体GABA电生理效应）的动物中，D2S，药物的运动和奖励作用是完整的。由于D2R基因的选择性剪接，D2L和D2S都是共表达的，因此通过使用经典敲除和/或药理学工具无法明确定义D2R的作用。因此，为了实现这一目标，我们产生了条件D2R小鼠突变体，其中可以选择性地从多巴胺能或纹状体神经元中切除D2R位点。当动物暴露于精神兴奋剂可卡因时，行为学、生物化学和免疫组织化学被提议来分析D2R位点特异性效应的丧失。使用这些不同的方法，我们将能够确定D2受体缺失在行为和细胞水平上的影响，并可能确定D2R缺陷小鼠滥用药物反应改变的分子机制。这项研究可能会导致新的治疗干预治疗成瘾。滥用药物成瘾是一个重大的社会和健康问题。为了能够设计治疗成瘾的干预措施，需要对药物在大脑中激活的分子机制有详细的了解。通过对复杂动物模型的分析，神经递质多巴胺如何改变大脑活动以应对精神兴奋剂可卡因的问题将得到解决。这可能会导致重要的新治疗发展。

DESCRIPTION (provided by applicant): Addiction is a major health and social problem. The dopaminergic system is highly solicited by drugs of abuse, as an increased release of dopamine is a hallmark of the effect of drug intake. The dopamine D2 receptor (D2R) is a key component of the dopaminergic system. Indeed, in addition to its postsynaptic wide and abundant distribution in the central nervous system, it also functions as autoreceptor in the control of dopamine synthesis and release. D2Rs also modulate release of other neurotransmitters from postsynaptic neurons acting as a presynaptic heteroreceptor. D2Rs are composed in vivo by two isoforms, D2L and D2S, generated from the same gene by alternative splicing. The aim of this proposal is to demonstrate that the presynaptic autoreceptor/heterosynaptic control mediated by dopamine D2 receptors exerts a principal role in the behavioral and cellular responses to drugs of abuse. This hypothesis is based on preliminary studies conducted in our laboratory showing that absence of D2 receptors signaling in mice (D2R-/-) strongly alters the response to psychostimulants and other abused drugs. On the contrary, in D2L-/- animals that do not express the D2L isoform of the receptor with postsynaptic functions (i.e. behavioral and cellular pharmacological responses to agonists/antagonists), but maintain the expression of the presynaptic/heterosynaptic receptor functions (i.e. control of DA release, cocaine-induced effects on striatal GABA electrophysiological effects), D2S, the motor and rewarding effects of drugs are intact. Both D2L and D2S are co-expressed, as a result of the alternative splicing of the D2R gene, thereby preventing a clear definition of the D2R role by the use of classical knockouts and/or by pharmacological tools. Thus, to achieve this aim we have generated conditional D2R mouse mutants, in which the selective ablation of D2R sites from dopaminergic or striatal neurons can be performed. Behavioral, biochemical and immunohistochemical studies are proposed to analyze loss of D2R site-specific effects when animals are exposed to the psychostimulant cocaine. Using these different approaches we will be able to determine the impact of loss of D2 receptors at the behavioral and cellular levels and possibly to identify the molecular mechanisms underlying the altered response to drugs of abuse found in D2R deficient mice. This research may lead to novel therapeutic intervention to treat addiction. PUBLIC HEALTH RELEVANCE Addiction to drugs of abuse is a major social and health problem. To be able to design therapeutic interventions to treat addiction, a detailed knowledge of the molecular mechanisms activated by drugs in the brain is requested. Through the analysis of sophisticated animal models, questions on how the neurotransmitter dopamine modifies brain activity in response to the psychostimulant cocaine will be addressed. This may lead to important new therapeutic developments.