Cocaine and monoamine transporters

描述(申请人提供)：可卡因滥用和成瘾仍然是一个严重的问题在世界上。目前，还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这种疾病的方法。可卡因有三个已知的高亲和力靶点，即多巴胺(DA)转运体(DAT)、5-羟色胺(5-羟色胺)转运体(SERT)和去甲肾上腺素(NE)转运体(NET)。当可卡因进入大脑时，它会阻止所有这三种转运蛋白，从而增加不同脑区的细胞外DA、5HT和NE，导致复杂的可卡因效应。研究每个转运蛋白作用的一种方法是产生缺失单个转运蛋白的基因敲除小鼠。这种方法的潜在问题是，为了补偿关键转运蛋白的完全移除而进行的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。我们正在产生一种携带转运蛋白突变体的敲入鼠系，该突变体对可卡因抑制不敏感，同时保持功能性的单胺摄取。我们已经产生了一个携带可卡因不敏感DAT突变体的敲入小鼠系，该突变体保持了相当大的摄取活性。在这些小鼠中，可卡因不再产生奖赏，这表明阻断DAT是可卡因奖赏所必需的。然而，DAT突变小鼠并没有提供关于Net和SERT在可卡因效应中所起作用的信息。这项研究的具体目的是(1)构建具有功能但对可卡因抑制不敏感的SERT和Net突变体；(2)用可卡因不敏感的转运蛋白突变体取代SERT或Net产生2个小鼠系；(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阻断是否也是可卡因奖励所必需的，或者它是增强或抑制可卡因奖励。对多巴胺、5-羟色胺和去甲肾上腺素系统如何调节可卡因奖赏和厌恶的精确了解可能提示潜在的药物靶点来调节可卡因奖赏和厌恶的强度和动态。抑制可卡因引起的快感和延长可卡因焦虑感的化合物可能会阻止可卡因的寻找和滥用。这些化合物将是开发可卡因成瘾药物治疗的极佳候选药物。

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.