MODULATION OF DOPAMINE AUTORECEPTOR FUNCTION BY COCAINE

描述(申请人摘要)： 这个项目的长期目标是定义 可卡因与突触前多巴胺能系统的相互作用。许多人 可卡因对行为的影响归因于它能阻止 中脑边缘神经元对多巴胺的再摄取。因此，增加了 细胞外多巴胺可能增强突触后传递和/或调节 已知突触前多巴胺受体抑制神经递质合成 以及进一步释放。此应用程序的具体目标是 通过聚焦于与以下相关的突触前事件来剖析这一系统 可卡因据称对多巴胺自身受体有调节作用。为此， 模型神经元系统是通过将永生的 克隆了D2和D3受体的中脑多巴胺产生细胞系。 为了检验D2样受体对不同的 自身受体的作用，转导的细胞系正在系统地 测试受体对合成和释放的调节作用。先前 我们已经证明，激动剂刺激D2和D3受体会导致 亚型特异性减少多巴胺的释放和合成。这些数据 暗示每种受体的特定作用，并暗示可卡因的作用 可能因受体亚型不同而不同。本提案中概述的研究 会不会1)检验这样一种假设，即不同的自身受体效应 D2和D3受体是由于不同的偶联机制所致；2)确定 D3脱敏的机理基础；3)检验假设 神经元原代培养多巴胺D2受体亚型可服务于ALL 这些功能：调节放电频率、多巴胺合成和多巴胺 释放；以及4)测试可卡因的急性和慢性影响 转基因细胞的自身受体功能与初级多巴胺能 文化。综上所述，这些研究将大大扩展我们的 正在努力了解复杂的受体/突触前效应器 强化和行为敏感化中的相互作用 可卡因的影响。

DESCRIPTION (Applicant's Abstract): The long term goal of this project is to define the consequences of the interaction of cocaine with presynaptic dopaminergic systems. Many of the behavioral effects of cocaine are attributed to its ability to block the reuptake of dopamine in mesolimbic neurons. Consequently, increased extracellular dopamine may enhance postsynaptic transmission and/or modulate presynaptic dopamine receptors known to inhibit neurotransmitter synthesis as well as further release. The specific aim of this application is to dissect this system by focussing on presynaptic events associated with cocaine's purported modulation of dopamine autoreceptors. Towards this end, model neuronal systems have been engineered by transfecting immortalized mesencephalic dopamine producing cell lines with cloned D2 and D3 receptors. To test the hypothesis that the D2-like receptors subserve different autoreceptor roles, the transfected cell lines are being systematically tested for receptor mediated effects on synthesis and release. Previously we have shown that agonist stimulation of D2 and D3 receptors leads to subtype specific reductions in dopamine release and synthesis. These data imply specific roles for each receptor and suggest the effects of cocaine may vary depending upon receptor subtype. Studies outlined in this proposal will 1 ) test the hypothesis that the differential autoreceptor effects of D2 and D3 receptors are due to distinct coupling mechanisms; 2) determine the mechanistic basis for D3 desensitization; 3) test the hypothesis that in primary cultures of neurons the dopamine D2 receptor subtype can serve all these functions: modulation of firing rate, dopamine synthesis and dopamine release; and 4) test the acute and chronic effects of cocaine on autoreceptor function in transfected cell lines and primary dopaminergic cultures. Taken together these studies will significantly extend our ongoing efforts to understand the complex receptor/presynaptic effector interactions involved in the reinforcing and behavioral sensitization effects of cocaine.