Role of D3 dopamine receptor in behavioral sensitization

描述（由申请人提供）：行为致敏，即重复用药后某些行为的渐进和持久增强，长期增强啮齿动物的运动能力。多巴胺通路在药物依赖和精神病中发挥重要作用，在致敏中也起关键作用。然而，个体多巴胺受体亚型在致敏中的作用尚未明确。D3多巴胺受体刺激抑制啮齿动物运动。D3受体的活性可以通过选择性剪接、截断的受体异构体（称为“D3nf”）的表达来调节，通过与全长亚基的二聚化来改变受体的定位和功能。我们研究的中心假设是：1.)通过降低D3受体介导的运动抑制的反应性，重复的D3受体刺激有助于敏化的发展；2.) D3nf表达的增加导致受体定位改变，随后释放d3受体介导的抑制，促进致敏表达。我们将用以下具体目标来检验这些假设。在Specific Aim 1中，我们确定了D3受体在对安非他明的行为致敏中的作用。我们通过确定多巴胺受体激动剂和拮抗剂对致敏性发展和D3受体异构体表达的影响，验证了对D3受体刺激的稳态代偿反应有助于改变D3受体剪接和致敏性发展的假设。在特异性目标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。该目的验证了致敏性的表达部分是由于D3介导的抑制释放，因此导致对D3受体拮抗剂的反应降低的假设。在特异性目标3中，我们将确定慢性安非他明给药对D3多巴胺受体表达的影响。我们将测量全长D3受体和D3nf mRNA的表达，并测量D3受体内化。本研究旨在验证慢性服用安非他明增加D3nf表达的假设，从而通过内化全长D3受体抑制全长D3受体功能。我们预计在致敏后，D3nf表达增加，D3受体内化增加。这一发现表明，替代剪接途径作为一种新的干预措施，可以防止致敏，并恢复d3介导的抑制功能，同时也表明了D3nf的生物学功能。集体;这些研究提供了一个新的假设的多方面的测试机制的长期变化的边缘介导的行为。这些结果可能为神经精神疾病提供新的干预措施，其中多巴胺已知发挥重要作用，包括精神病和药物依赖。值得注意的是，这些研究可能还阐明了一种以前未被认识到的调节受体脱敏和转运的机制，这种机制与其他受体系统和病理状况有关。

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.