MODULATION OF DOPAMINE AUTORECEPTOR FUNCTION BY COCAINE

这个项目的长期目标是定义分子间的相互作用 可卡因和多巴胺能系统。的许多行为影响 可卡因被归因于它能阻止多巴胺在体内的再摄取。 中脑边缘神经元。因此，细胞外多巴胺的增加可能 增强突触后传递和/或调节突触前多巴胺 已知的抑制神经递质合成的受体以及进一步的 放手。本应用程序的具体目标是通过以下方式剖析该系统 关注与可卡因据称有关的突触前事件 多巴胺自身受体的调节。为了达到这个目的，模型神经元 通过将永生化的中脑细胞 具有克隆的D2和D3受体的多巴胺产生细胞系。而当 传统上，D2受体与自身受体功能有关， 目前尚不清楚D2样亚型中的哪一种服从于 释放和/或合成。来检验类D2病毒的假设 受体发挥不同的作用，转导的细胞系将 系统测试受体介导的合成和 放手。初步结果表明，激动剂刺激D2和D3 受体导致亚型特异性多巴胺释放减少和 综合。这些数据暗示了每个受体的特定作用，并提示 可卡因的作用可能因受体亚型不同而不同。研究 在这份提案中概述的L)将决定各种D2的效果 激动剂对AS细胞株中多巴胺释放的影响 以及百日咳毒素、阳离子通道、 调节这一反应的脱敏和磷酸化途径。 2)确定受体刺激和脱敏在 酪氨酸羟基酶活性及其变化对多巴胺合成的影响 处于酪氨酸羟化酶磷酸化状态。各种不同的角色 信号转导通路将通过使用特定蛋白质进行测试 改变多巴胺自身调节的激酶和磷酸酶抑制剂 综合。在这两种情况下，受体与特定的GTP结合 蛋白质将接受使用突变G蛋白的测试。3)测试的效果 急、慢性可卡因对自身受体功能的影响 综合范式。这些研究直接影响到 理解突触前强化和突触前机制 可卡因的行为敏化作用。

The long term goal of this project is to define the molecular interactions of cocaine with 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. While traditionally D2 receptors have been implicated in autoreceptor function, it is not known which of the D2-like subtypes subserves autoregulation of release and/or synthesis. To test the hypothesis that the D2-like receptors subserve different roles, the transfected cell lines will be systematically tested for receptor mediated effects on synthesis and release. Preliminary results show that agonist stimulation ofD2 and D3 receptors lead 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 l) determine the effect of various D2 agonists on dopamine release in the individual transfected cell lines as well as the general roles of pertussis toxin, cation channels, desensitization and phosphorylation pathways in modulating this response. 2) Determine the role of receptor stimulation and desensitization on dopamine synthesis by measuring tyrosine hydroxylase activity and changes in the state of tyrosine hydroxylase phosphorylation. The roles of various signal transduction pathways will be tested by using specific protein kinase and phosphatase inhibitors to alter autoregulation of dopamine synthesis. In either case receptor coupling to specific GTP binding proteins will be tested for using mutant G proteins. 3) Test the effect of acute and chronic cocaine on autoreceptor function in both the release and synthesis paradigms. These studies have direct implications for understanding the presynaptic mechanisms involved in the reinforcing and behavior sensitization effects of cocaine.