Makos Monique A, Han Kyung-An, Heien Michael L, Ewing Andrew G
Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
ACS Chem Neurosci. 2010 Jan 20;1(1):74-83. doi: 10.1021/cn900017w.
Dopamine neurotransmission is thought to play a critical role in addiction reinforcing mechanisms of drugs of abuse. Electrochemical techniques have been employed extensively for monitoring in vivo dopamine changes in the brains of model organisms including rats, mice, and primates. Here, we investigated the effects of several stimulants on dopamine clearance using recently developed microanalytical tools for in vivo electrochemical measurements of dopamine in the central nervous system of Drosophila melanogaster. A cylindrical carbon-fiber microelectrode was placed in the protocerebral anterior medial region of the Drosophila brain (an area dense with dopamine neurons) while a micropipette injector was positioned to exogenously apply dopamine. Background-subtracted fast-scan cyclic voltammetry was carried out to quantify changes in dopamine concentration in the adult fly brain. Clearance of exogenously applied dopamine was significantly decreased in the protocerebral anterior medial area of the wild-type fly following treatment with cocaine, amphetamine, methamphetamine, or methylphenidate. In contrast, dopamine uptake remained unchanged when identical treatments were employed in fumin mutant flies that lack functional dopamine transporters. Our in vivo results support in vitro binding affinity studies that predict these four stimulants effectively block normal Drosophila dopamine transporter function. Furthermore, we found 10 muM to be a sufficient physiological cocaine concentration to significantly alter dopamine transporter uptake in the Drosophila central nervous system. Taken together, these data indicate dopamine uptake in the Drosophila brain is decreased by psychostimulants as observed in mammals. This validates the use of Drosophila as a model system for future studies into the cellular and molecular mechanisms underlying drug addiction in humans.
多巴胺神经传递被认为在滥用药物的成瘾强化机制中起关键作用。电化学技术已被广泛用于监测包括大鼠、小鼠和灵长类动物在内的模式生物大脑中的体内多巴胺变化。在此，我们使用最近开发的用于在黑腹果蝇中枢神经系统中对多巴胺进行体内电化学测量的微分析工具，研究了几种兴奋剂对多巴胺清除的影响。将圆柱形碳纤维微电极放置在果蝇大脑的原脑前内侧区域（一个多巴胺神经元密集的区域），同时将微量移液器注射器定位以外源施加多巴胺。进行背景扣除快速扫描循环伏安法以量化成年果蝇大脑中多巴胺浓度的变化。在用可卡因、苯丙胺、甲基苯丙胺或哌醋甲酯处理后，野生型果蝇原脑前内侧区域中外源施加的多巴胺清除率显著降低。相比之下，当在缺乏功能性多巴胺转运蛋白的福明突变果蝇中采用相同处理时，多巴胺摄取保持不变。我们的体内结果支持体外结合亲和力研究，该研究预测这四种兴奋剂有效阻断正常果蝇多巴胺转运蛋白功能。此外，我们发现10μM是足以显著改变果蝇中枢神经系统中多巴胺转运蛋白摄取的生理可卡因浓度。综上所述，这些数据表明，如在哺乳动物中观察到的那样，精神兴奋剂会降低果蝇大脑中的多巴胺摄取。这验证了将果蝇用作未来研究人类药物成瘾潜在细胞和分子机制的模型系统。
