Exploring a role for organic transporter 3 in the mechanism of action of drugs of abuse

摘要 可卡因和酒精的共同滥用是最常见和危险的药物组合之一， 同时使用这些药物是导致紧急住院的主要原因。因此，这种药物组合不是 仅对个人用户的健康构成严重威胁，但对公众健康造成重大负担。目前，没有 对可卡因和乙醇成瘾的有效治疗，强调了解 这种高度成瘾的药物配对的机制基础，以发现新的治疗靶点 干预。众所周知，可卡因和乙醇都会增加细胞外多巴胺(DA)的水平， 5-羟色胺(5-羟色胺)和去甲肾上腺素(NE)，这两种生物胺类神经递质与 具有奖励性质的药物。可卡因通过抑制高亲和力、低容量的转运蛋白来实现这一点 这些神经递质分别为DAT、SERT和NET。然而，乙醇的作用机制 目前还不清楚是否会这样做。已知乙醇抑制DA、5-羟色胺和去甲肾上腺素的摄取，然而我们发表的数据显示， 结合文献证据，表明这种抑制是DAT、SERT和网络无关的。有机食品 阳离子转运蛋白3(Oct3)是一种低亲和力、高容量的多巴胺、5-羟色胺和去甲肾上腺素的转运蛋白 作为生物胺动态平衡调节的重要参与者。有趣的是，最近的报告显示 Oct3的阻断剂皮质酮增强可卡因诱导的DA信号并促进恢复 通过Oct3依赖机制寻找可卡因。此外，我们还发现Oct3的表达增加 在缺乏SERT(-/-)小鼠中，乙醇和皮质酮都抑制SERT-/-小鼠的5-羟色胺清除，以 比野生型要大得多。总而言之，这些发现增加了这样一种可能性 乙醇可能与Oct3相互作用以抑制生物胺的摄取，从而增加成瘾性 可卡因的特性，以及宣传这些药物的同时使用。为此目的，在 这一探索性的R21将测试压倒一切的假设，即乙醇增加的一个机制 细胞外多巴胺、5-羟色胺和去甲肾上腺素是通过Oct3抑制它们的摄取的，这种抑制增强了 可卡因产生的生物胺增加，这阻碍了它们通过DAT、SERT和NET的摄取。 重要的是，我们将确定乙醇增强奖励特性的能力对Oct3的依赖 可卡因。我们将使用药理学和遗传学方法，结合体内神经化学，以及 与奖励相关的行为分析。无论这些探索性研究的结果如何，结果都将 关于乙醇抑制生物来源的摄取的机制的基础知识空白(S) 胺化并增强可卡因的奖励作用。这些研究的结果将提高我们对 使酒精和可卡因同时使用的滥用可能性如此之高的机制。重要的是 这些研究将形成一个重要的平台，在此基础上进行更大规模的探索新分子的研究 目标可能是10月3日，用于治疗酒精和可卡因滥用的药物。

ABSTRACT Co-abuse of cocaine and alcohol is one of the most common, and dangerous drug pairings, as evidenced by their concurrent use being a major cause for emergency hospitalization. Thus, this drug combination is not only a serious health threat to the individual user, but a major public health burden. Currently, there are no effective treatments for addiction to cocaine and ethanol, underscoring the vital need to understand the mechanistic basis of this highly addictive drug pairing in order to discover new targets for therapeutic intervention. It is well-known that cocaine and ethanol each increase extracellular levels of dopamine (DA), serotonin (5-HT), and norepinephrine (NE), biogenic amine neurotransmitters that are strongly linked to the rewarding properties of drugs. Cocaine does this by inhibiting the high-affinity, low-capacity transporters for these neurotransmitters, DAT, SERT, and NET, respectively. However, the mechanisms by which ethanol does so are unclear. It is known that ethanol inhibits uptake of DA, 5-HT, and NE, however our published data, together with literature evidence, show this inhibition to be DAT-, SERT-, and NET-independent. Organic cation transporter 3 (OCT3) is a low-affinity, high-capacity transporter for DA, 5-HT, and NE, and is emerging as an important player in regulation of biogenic amine homeostasis. Interestingly, recent reports show that corticosterone, a blocker of OCT3, enhances cocaine-induced DA signaling and potentiates reinstatement of cocaine seeking via an OCT3-dependent mechanism. Moreover, we found that OCT3 expression is increased in mice lacking SERT (-/-), and that ethanol, and corticosterone, both inhibit 5-HT clearance in SERT-/- mice to a much greater extent than in their wild-type counterpart. Together, these findings raise the possibility that ethanol may interact with OCT3 to inhibit uptake of biogenic amines, thereby increasing the addictive properties of cocaine, and propagating the concurrent use of these drugs. To this end, the studies proposed in this exploratory R21 will test the overarching hypothesis that one mechanism by which ethanol increases extracellular DA, 5-HT and NE is by inhibition of their uptake via OCT3, and that this inhibition enhances the increase in biogenic amines produced by cocaine, which blocks their uptake via DAT, SERT and NET. Importantly, we will determine the OCT3-dependency of ethanol’s ability to enhance the rewarding properties of cocaine. We will use pharmacological and genetic approaches, combined with in vivo neurochemistry, and behavioral assays relevant for reward. Regardless of the outcome of these exploratory studies, results will fill fundamental knowledge gaps about the mechanism(s) through which ethanol inhibits uptake of biogenic amines and enhances rewarding effects of cocaine. Results from these studies will improve our understanding of mechanisms that make the abuse potential of concurrent alcohol and cocaine use so high. Importantly, these studies will form an essential platform on which to base larger scale studies probing novel molecular targets, putatively OCT3, for medications to treat abuse of alcohol and cocaine.