Role of D3 dopamine receptor in behavioral sensitization

描述(由申请人提供)：行为敏感化，重复使用药物后某些行为的渐进和持久的增强，以一种长期的方式增强啮齿动物的运动。同样的多巴胺通路在药物依赖和精神病中起着重要作用，在致敏作用中也起着关键作用。然而，个别多巴胺受体亚型在致敏中的作用尚未明确。刺激D3多巴胺受体抑制啮齿动物的运动。D3受体的活性可以通过表达选择性剪接的、截短的受体亚型(称为“D3nf”)来调节，通过与全长亚基的二聚化改变受体的定位和功能。我们研究的中心假设是1。)重复的D3受体刺激通过降低D3受体介导的运动抑制的响应性来促进敏化的发展；D3nf的表达增加指导了受体定位的改变和随后D3受体介导的抑制的释放，有助于致敏的表达。我们将用以下具体目标来检验这些假设。在具体目标1中，我们确定了D3受体在苯丙胺行为敏化中的作用。我们通过测定多巴胺受体激动剂和拮抗剂对致敏发展和D3受体亚型表达的影响，验证了对D3受体刺激的动态平衡、代偿反应有助于改变D3受体剪接和致敏发展的假说。在特定目标2中，我们将评估慢性给药后对D3受体拮抗剂的行为反应。我们将测量D3受体阻断后的行为反应，使用D3选择性药物作为测量D3受体功能的工具。这一目的验证了一种假设，即致敏表达的部分原因是D3介导的抑制作用的释放，从而导致对D3受体拮抗剂的反应降低。在具体目标3中，我们将确定长期服用苯丙胺对D3多巴胺受体表达的影响。我们将检测全长D3受体和D3nf mRNA的表达，并检测D3受体的内化。这一目的验证了一种假设，即长期服用苯丙胺会增加D3nf的表达，从而通过内化全长受体来抑制全长D3受体的功能。我们预计在致敏后，D3nf表达增加，D3受体内化增加。这一发现将提示可选择的剪接途径作为一种新的干预措施来防止致敏，以及恢复D3介导的抑制功能，也将提示D3nf的生物学功能。总而言之，这些研究对边缘调节行为长期变化背后的机制提供了一个新的假设的多方面检验。这些结果可能建议对神经精神疾病进行新的干预，已知多巴胺在其中发挥重要作用，包括精神病和药物依赖。值得注意的是，这些研究还可能阐明以前未知的调节受体脱敏和运输的机制，这些机制与其他受体系统和病理条件有关。

DESCRIPTION (provided by applicant): Behavioral sensitization, the progressive and enduring enhancement of certain behaviors following repetitive drug use, augments rodent locomotion in a long-standing fashion. The same dopamine pathways playing an important role in drug dependence and psychosis also play a critical role in sensitization. The role of individual dopamine receptor subtypes in sensitization, however, has not been clearly identified. D3 dopamine receptor stimulation inhibits rodent locomotion. D3 receptor activity may be regulated through expression of an alternatively spliced, truncated receptor isoform (termed "D3nf") altering receptor localization and function via dimerization with the full-length subunit. The central hypotheses for our research are that 1.) repetitive D3 receptor stimulation contributes to development of sensitization through decreased responsivity of D3 receptor-mediated locomotor inhibition; and 2.) increased D3nf expression directs altered receptor localization and subsequent release of D3-receptor mediated inhibition, contributing to expression of sensitization. We will test these hypotheses with the following Specific Aims. In Specific Aim 1,we identify the role of D3 receptors in behavioral sensitization to amphetamine. We test the hypothesis that a homeostatic, compensatory response to D3 receptor stimulation contributes to altered D3 receptor splicing and the development of sensitization by determining the effect of dopamine receptor agonists and antagonists on development of sensitization and D3 receptor isoform expression. In Specific Aim 2, we will evaluate behavioral response to D3 receptor antagonists following chronic drug administration. We will measure the behavioral response to D3 receptor blockade, using D3-selective drugs as a tool to measure D3 receptor function. This aim tests the hypothesis that expression of sensitization results in part from release of D3-mediated inhibition, therefore resulting in decreased response to D3 receptor antagonist. In Specific Aim 3, we will determine the consequences of chronic amphetamine administration on D3 dopamine receptor expression. We will measure expression of both full-length D3 receptor and D3nf mRNA, and also measure D3 receptor internalization. This aim tests the hypothesis that chronic amphetamine administration increases D3nf expression, thereby inhibiting full-length D3 receptor function by internalizing the full-length receptor. We expect to demonstrate increased D3nf expression, and increased D3 receptor internalization, following sensitization. This finding would suggest alternative splicing pathways as a novel intervention to prevent sensitization, as well as restore D3-mediated inhibitory function, and would also suggest a biological function for D3nf. Collectively; these studies provide a multi-faceted test of a novel hypothesis of the mechanism underlying long-standing changes in limbic-mediated behaviors. These outcomes may suggest new interventions for neuropsychiatric conditions in which dopamine is known to play an important role, including psychosis and drug dependence. Significantly, these studies may also elucidate a previously unrecognized mechanism regulating receptor desensitization and trafficking relevant to other receptor systems and pathological conditions.