Individual Differences in Cocaine Activation/Reward and the Dopamine Transporter

描述（由申请人提供）：本申请要求更新nida赞助的MERIT奖作为R01。总体目标是了解为什么个体在可卡因诱导的激活方面存在差异，特别是，1)多巴胺（DA）转运体（DAT）如何导致这种差异的反应性，以及2)这种个体差异如何预测可卡因滥用倾向。根据低剂量可卡因注射后不同的野外运动活动，成年雄性Sprague-Dawley大鼠可分为低可卡因反应或高可卡因反应（lcr或hcr）。可卡因激活的这些初始差异部分可以通过可卡因如何有效地抑制背纹状体（dSTR）和伏隔核（NAc）的DAT来解释。这种分类也预测了与奖励和强化相关的可卡因诱导的重复行为，其中lcr比hcr更表现出运动敏化、条件位置偏好和自我使用可卡因的动机。不同的LCR/HCR DAT抑制预期会导致细胞外DA水平和DA受体(R)刺激的差异。目的1将使用i)体内微透析来定义dSTR和NAc核心的内源性细胞外DA与lcr和hcr中急性和反复可卡因诱导的运动激活之间的总体关系；ii)最新的体内电化学记录技术来评估自由行为lcr和hcr中dSTR和NAc亚区（核心和壳）中可卡因诱导的内源性细胞外DA水平的实时变化。目标2将探讨lcr和hcr在可卡因诱导的1)dSTR和NAc的快速数据调节（贩运）和2)可能有助于解释行为差异的长期数据调节和DA R调节方面的潜在差异。这些实验将测量开放场活性、细胞表面DAT水平、[3H]DA摄取动力学和孤儿G蛋白偶联受体GPR37的水平。体外放射配体结合的定量放射自显影分析将用于评估dat、D1Rs、D2Rs和激动剂刺激的g蛋白偶联的调节。目的3将通过测量LCR/HCR分类如何预测可卡因的成瘾相关效应：1)在获得可卡因自我给药和可卡因预暴露期间的致敏性；2)在递进比例强化计划下测量的对可卡因动机效应的致敏性；3)在线索引发的对可卡因的反应恢复和在二级强化计划下的反应背景下的激励敏感性。并发体内电化学记录将用于解决自我给药实验中的特定问题。总之，这些结果将提供新的见解，解释为什么对可卡因运动激活的初始不敏感与更“容易上瘾”的现象类型有关，快速和长期的DAT适应及其后果如何促成这种个体差异，以及致敏如何影响可卡因自我给药。了解可卡因滥用/成瘾个体差异的生物学基础对治疗这种疾病具有根本重要性。每个人对可卡因滥用和成瘾的易感性明显不同。该项目将使用动物模型来探索正常大脑化学的个体差异如何导致可卡因诱导的激活和成瘾样行为的变异性。了解可卡因滥用/成瘾个体差异的生物学基础，对于开发治疗并最终预防这一破坏性脑部疾病和公共卫生问题的新方法至关重要。

DESCRIPTION (provided by applicant): This application requests renewal of a NIDA-sponsored MERIT Award as a R01. The overall goal is to under- stand why individuals differ in cocaine-induced activation and, specifically, i) how the dopamine (DA) trans- porter (DAT) contributes to this differential responsiveness and ii) how this individual variability is predictive of cocaine abuse liability. Adult outbred male Sprague-Dawley rats can be classified as either low or high cocaine responders (LCRs or HCRs, respectively) based on their differential open-field locomotor activity following a low dose cocaine injection. These initial differences in cocaine activation are explained, in part, by how effectively cocaine inhibits the DAT in dorsal striatum (dSTR) and nucleus accumbens (NAc). This classification also predicts repeated cocaine-induced behaviors associated with reward and reinforcement, in that LCRs, more than HCRs, exhibit locomotor sensitization, conditioned place preference and motivation to self- administer cocaine. Differential LCR/HCR DAT inhibition would be expected to result in differences in extra- cellular DA levels and DA receptor (R) stimulation. Aim 1 will use i) in vivo microdialysis to define the overall relationship between endogenous extracellular DA in dSTR and NAc core and acute and repeated cocaine- induced locomotor activation in LCRs and HCRs and ii) new state-of-the-art in vivo electrochemical recording technology to assess real-time changes in cocaine-induced endogenous extracellular DA levels in dSTR and subregions of NAc (core and shell) in freely-behaving LCRs and HCRs. Aim 2 will explore potential differences between LCRs and HCRs in cocaine-induced i) rapid DAT regulation (trafficking) in dSTR and NAc and ii) longer-term DAT and DA R regulation that could help to explain the behavioral differences. These experiments will measure open-field activity, cell surface DAT levels, [3H]DA uptake kinetics, and levels of the orphan G- protein-coupled receptor GPR37. Quantitative autoradiographic analysis of in vitro radioligand binding will be used to assess regulation of DATs, D1Rs, D2Rs and agonist-stimulated G-protein coupling. Aim 3 will deter- mine how LCR/HCR classification predicts addiction-related effects of cocaine by measuring i) sensitization during acquisition of cocaine self-administration and cocaine pre-exposure, ii) sensitization to motivational effects of cocaine measured under a progressive ratio schedule of reinforcement, and iii) incentive sensiti- zation in the context of cue-elicited reinstatement of responding for cocaine and responding under a second- order schedule of reinforcement. Concurrent in vivo electrochemical recording will be used to address particular questions in the self-administration experiments. Together, the results will provide novel insights as to why initial insensitivity to cocaine locomotor activation is associated with the more "addiction prone" pheno- type, how both rapid and longer-term DAT adaptations and their consequences contribute to this individual variability, and how sensitization impacts cocaine self-administration. Understanding the biological bases for individual differences in cocaine abuse/addiction is of fundamental importance for treating this disease. Individuals vary markedly in their vulnerability to cocaine abuse and addiction. This project will use an animal model to explore how individual differences in normal brain chemistry can contribute to variability in cocaine-induced activation and addiction-like behaviors. Understanding the biological bases for individual differences in cocaine abuse/addiction is of fundamental importance for developing new ways to treat, and ultimately prevent, this devastating brain disease and public health problem.