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。多巴胺能系统被滥用的药物高度吸引，因为多巴胺的释放增加是药物摄入效果的标志。多巴胺D2受体（D2 R）是多巴胺能系统的关键组成部分。事实上，除了其在中枢神经系统中的突触后广泛和丰富的分布外，它还作为自身受体控制多巴胺的合成和释放。D2 R还调节作为突触前异源受体的突触后神经元的其他神经递质的释放。D2 R在体内由两种同种型D2 L和D2 S组成，这两种同种型通过选择性剪接由相同基因产生。该建议的目的是证明多巴胺D2受体介导的突触前自身受体/异突触控制在滥用药物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，表明小鼠中D2受体信号传导的缺失（D2 R-/-）强烈改变了对精神兴奋剂和其他滥用药物的反应。相反，在不表达具有突触后功能的受体的D2 L同种型的D2 L-/-动物中，（即对激动剂/拮抗剂的行为和细胞药理学反应），但维持突触前/异突触受体功能的表达（即DA释放的控制，可卡因诱导的对纹状体GABA电生理效应的影响），D2 S，药物的运动和奖励效应是完整的。由于D2 R基因的选择性剪接，D2 L和D2 S都是共表达的，从而阻止了通过使用经典敲除和/或通过药理学工具对D2 R作用的明确定义。因此，为了实现这一目标，我们已经产生了条件D2 R小鼠突变体，其中可以进行多巴胺能或纹状体神经元的D2 R位点的选择性消融。行为，生物化学和免疫组织化学研究提出了分析损失的D2 R位点特异性的影响时，动物暴露于精神兴奋剂可卡因。使用这些不同的方法，我们将能够确定在行为和细胞水平的D2受体的损失的影响，并可能确定潜在的分子机制改变的药物滥用在D2 R缺陷小鼠中发现的反应。这项研究可能会导致新的治疗干预来治疗成瘾。对滥用药物上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，需要详细了解大脑中药物激活的分子机制。通过对复杂的动物模型的分析，将解决神经递质多巴胺如何改变大脑活动以响应精神兴奋剂可卡因的问题。这可能导致重要的新的治疗发展。

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.