NOVEL PROBES FOR THE DOPAMINE TRANSPORTER

多巴胺转运体一直是 潜在的可卡因滥用疗法的发展。尽管 抑制多巴胺再摄取很可能是过于简单化的 对于可卡因的成瘾特性的解释，它仍然是 负责加固效果的最重要的机械候选人 这种滥用的药物。新型探头的研究进展 结构不同但保留的多巴胺转运体 可卡因的神经化学等效性是我们研究的重点。 程序。我们对这些化合物特别感兴趣 对多巴胺转运体的亲和力与可卡因相同或更高 但在药物滥用的动物模型中并不像可卡因那样。这些 化合物将有助于表征多巴胺的结合域。 转运蛋白和允许确定的功能相关性 那些网站。最终，可以预见，一种化合物可能是 它能与多巴胺转运蛋白结合并防止可卡因 在没有可卡因本身的上瘾倾向的情况下摆脱束缚。 我们探索了基于两个化合物的新型类似物的设计和合成 多巴胺摄取抑制剂的分类及其体外评价 (放射性配基结合分析和抑制[~3H]多巴胺摄取)和 在体内(小鼠的运动活动，大鼠的药物辨别和 猴子的自我管理研究)。第一类化合物 以3-α-(二苯基甲氧基托烷)(苯并托品)为基础。上一首 该分子3位上的化学修饰使 发现一类有效的多巴胺摄取抑制剂 与M受体的高亲和力结合，但具有高度选择性 关于5-羟色胺和去甲肾上腺素转运体。这些化合物 通常会阻止多巴胺的再摄取，可卡因也是如此，但没有 作为运动兴奋剂是有效的，在这两种药物中都不像可卡因一样 药物歧视或自我给药研究。为了试图 消除这些化合物的毒扁豆碱拮抗剂特性 合成了大系列N-取代4‘，4@-二氟类似物。 其中许多化合物在多巴胺上保持高亲和力结合。 转运蛋白，但显示亲和力显著下降 毒鼠碱受体。对这些化合物的行为评估，如 与上一系列并没有显示出类似可卡因的行为 侧写。此外，几个N-取代的类似物没有 增强可卡因的作用，就像大多数其他多巴胺摄取一样 已有证据表明，抑制剂和毒扁豆碱拮抗剂能起到作用。 药代动力学分析和慢性研究目前正在进行 正在进行进一步鉴定这些化合物的药理作用 以及它们作为药物疗法的潜力。此外，125i- N-丁基苯基取代4‘，4@-二氟的叠氮衍生物 苯并托品已经被制备出来，并被证明与 克隆的多巴胺转运体。这个亲光性标签将被使用 在未来的研究中，以确定这种跨膜螺旋 一类化合物结合，并将结合结构域与 以可卡因和GBR 12909为基础的光亲和配体标记。 已经对第二类化合物进行了大量的化学修饰 基于多巴胺摄取抑制剂/西格玛配体利姆卡唑的化合物 这会减弱可卡因诱导的运动活动。 咔唑环系和末端的取代反应 已经制造出了哌嗪氮。到目前为止，结构活性 相互关系表明，多巴胺转运体非常敏感 这种分子结构的变化，以及大多数的修饰 导致结合亲和力降低。然而，有几个类比 的亲和力相同或略高 多巴胺转运体优于利马卡唑(Ki=60-260 nm)。这些化合物 还评估了它们在sigma 1和1的结合亲和力 2受体。选定的化合物已经进行了行为评估和 到目前为止，像母体利姆卡唑一样，他们无法证明可卡因- 比如行为特征。可卡因相互作用的研究正在进行中。 此外，一种基于利姆卡唑的不可逆配体已经被 被发现并有望成为一种重要的研究工具 鉴定多巴胺转运体上的高亲和力和低亲和力 。

The dopamine transporter has been a primary molecular target for the development of potential cocaine abuse therapeutics. Although the inhibition of dopamine reuptake is likely to be an oversimplified explanation for the addictive properties of cocaine, it remains the foremost mechanistic candidate responsible for the reinforcing effects of this drug of abuse. The development of novel probes for the dopamine transporter that are structurally dissimilar but retain neurochemical equivalence to cocaine is the focus of our research program. We are particularly interested in those compounds that bind to the dopamine transporter with equal or higher affinity than cocaine but are not cocaine-like in animal models of drug abuse. These compounds will help characterize binding domains on the dopamine transporter and allow the determination of functional correlates to those sites. Ultimately, it is envisioned that a compound may be developed that binds to the dopamine transporter and prevents cocaine from binding without having the addiction liability of cocaine itself. We have explored the design and synthesis of novel analogs based on two classes of dopamine uptake inhibitors and have evaluated them in vitro (radioligand binding assays and inhibition of [3H]dopamine uptake) and in vivo (locomotor activity in mice, drug discrimination in rats and self administration studies in monkeys). The first class of compounds are based on 3-alpha-(diphenylmethoxytropane (benztropine). Previous chemical modification at the 3-position of this molecule allowed the discovery of a potent class of dopamine uptake inhibitors that retained high affinity binding at muscarinic receptors but were highly selective over serotonin and norepinephrine transporters. These compounds typically blocked dopamine reuptake, as does cocaine, but were not efficacious as locomotor stimulants and were not cocaine-like in either drug discrimination or self administration studies. In an attempt to eliminate the muscarinic antagonist properties of these compounds, a large series of N-substituted 4',4@-difluoro analogs were prepared. Many of these compounds retained high affinity binding at the dopamine transporter but demonstrated a significant decrease in affinity for muscarinic receptors. Behavioral evaluation of these compounds, as with the previous series did not demonstrate a cocaine-like behavioral profile. Further, several of the N-substituted analogs did not potentiate the effects of cocaine, as most other dopamine uptake inhibitors and muscarinic antagonists have been shown to do. Pharmacokinetic analysis as well as chronic studies are currently underway to further characterize the pharmacology of these compounds and their potential as pharmacotherapeutics. In addition, an 125I- azido- derivative of the N-butylphenyl substituted 4',4@-difluoro benztropine has been prepared and shown to irreversibly interact with the cloned dopamine transporter. This photoaffinity label will be used in future studies to determine the transmembrane helices at which this class of compounds binds and compare the binding domains with those labeled by photoaffinity ligands based on cocaine and GBR 12909. Numerous chemical modifications have been made to a second class of compounds, based on rimcazole, a dopamine uptake inhibitor/sigma ligand that attenuates the locomotor activity induced by cocaine. Substitutions at the carbazole ring system as well as at the terminal piperazine nitrogen have been made. Thusfar, structure-activity relationships suggest that the dopamine transporter is very sensitive to structural changes in this molecule, with most modifications resulting in a decrease in binding affinity. However, several analogs were discovered to have equal or slightly higher affinity at the dopamine transporter than rimcazole (Ki=60-260 nM). These compounds have also been evaluated for their binding affinities at sigma 1 and 2 receptors. Selected compounds have been evaluated behaviorally and so far, like the parent rimcazole they fail to demonstrate a cocaine- like behavioral profile. Cocaine-interaction studies are underway. In addition, an irreversible ligand based on rimcazole has been discovered and promises to be an important research tool with which to characterize high and low affinity sites on the dopamine transporter .