Cocaine and monoamine transporters

描述（由申请人提供）：可卡因滥用和成瘾仍然是世界上的一个严重问题。目前，没有有效的药物治疗这种精神障碍。我们的长期目标是了解可卡因成瘾的机制，以便开发有效的治疗方法。可卡因有三个已知的高亲和力靶点，多巴胺（DA）转运蛋白（DAT）、血清素（5HT）转运蛋白（SERT）和去甲肾上腺素（NE）转运蛋白（NET）。当可卡因进入大脑时，它会阻断所有三种转运体，从而增加大脑不同区域的细胞外DA、5HT和NE，导致复杂的可卡因效应。研究每种转运蛋白作用的一种方法是产生删除单个转运蛋白的敲除小鼠。这种方法的潜在问题是，为了补偿关键转运体的完全移除，适应性变化可能会显著改变奖励途径。我们正在采用另一种方法。我们正在产生携带转运体突变体的敲入小鼠系，该突变体对可卡因抑制不敏感，同时维持功能性单胺摄取。我们已经产生了一种携带可卡因不敏感DAT突变体的敲入小鼠系，该突变体保留了大量的摄取活性。在这些小鼠中，可卡因不再产生奖励，这表明DAT阻断对可卡因奖励是必要的。然而，DAT突变小鼠没有提供关于NET和SERT在可卡因效应中的作用的信息。该研究的具体目的是：(1)构建SERT和NET的突变体，这些突变体具有功能，但对可卡因抑制不敏感；(2)产生2个小鼠系，其SERT或NET被可卡因不敏感转运体突变体取代；(3)分析敲入小鼠对可卡因的反应。这项研究将告诉我们NET或SERT阻断是否对可卡因奖励也是必要的，或者它增强或抑制可卡因奖励。对DA、5HT和NE系统如何调节可卡因奖励和厌恶的精确了解，可能会提示调节可卡因奖励和厌恶的强度和动态的潜在药物靶点。抑制可卡因引起的欣快感和延长可卡因焦虑的化合物可能会阻止可卡因的寻找和滥用。这些化合物将成为开发可卡因成瘾药物治疗的优秀候选药物。

DESCRIPTION (provided by applicant): Cocaine abuse and addiction continue to be a serious problem in the world. Currently, there is no effective pharmacological treatment for this mental disorder. Our long term goal is to understand the mechanism of cocaine addiction in order to develop effective treatments for this disorder. Cocaine has three known high affinity targets, the dopamine (DA) transporter (DAT), the serotonin (5HT) transporter (SERT), and the norepinephrine (NE) transporter (NET). When cocaine enters the brain it blocks all three transporters and thus increases extracellular DA, 5HT, and NE in various brain regions, resulting in complex cocaine effects. One way to study the role of each transporter is to generate knockout mice with individual transporters deleted. The potential problem with this approach is that adaptive changes to compensate for the complete removal of the critical transporter may alter the reward pathway significantly. We are employing an alternative approach. We are generating knock-in mouse lines carrying a transporter mutant that is insensitive to cocaine inhibition while maintaining functional monoamine uptake. We have generated a knock-in mouse line carrying a cocaine-insensitive DAT mutant that retains substantial uptake activity. In these mice, cocaine no longer produces reward, suggesting that DAT blockade is necessary for cocaine reward. However, DAT mutant mice do not provide information about the roles of NET and SERT in cocaine effects. The specific aims of the proposed study is (1) to construct mutants of SERT and NET that are functional but insensitive to cocaine inhibition; (2) to generate 2 mouse lines with their SERT or NET replaced by the cocaine-insensitive transporter mutants; and (3) to analyze the cocaine responses by the knock-in mice. This study will tell us whether NET or SERT blockade is also necessary for cocaine reward, or it enhances or dampens cocaine reward. Precise knowledge on how DA, 5HT, and NE systems modulate cocaine reward and aversion may suggest potential drug targets to modulate the intensity and dynamics of cocaine reward and aversion. Compounds that dampen the cocaine-induced euphoria and prolong cocaine dysphoria may discourage cocaine seeking and abuse. These compounds would be excellent drug candidates for the development of pharmacological treatment for cocaine addiction.