Action of psychostimulant drugs on neuronal intrinsic excitability and drug-seeking behavior

毒瘾是一种慢性精神障碍，给成瘾者的生活带来巨大负担， 他们的家庭和整个社会。重要的是，相当大比例的吸毒者仍然抵制 治疗。针对成瘾常规机制以外的机制的多样化药物治疗 涉及多巴胺(DA)和单胺信号转导可以弥补这一差距。在这里，我们打算研究一部小说 对慢性可卡因的长期神经适应是由一种非规范的、DA非依赖性的 机制。慢性可卡因引起核团固有兴奋性(放电率)持续下降 伏隔壳(NAcSh)神经元。这种适应是由Sigma-1蛋白(σ1；又称Sigma-1)介导的。SIG-1R)，a 一种伴侣，其活性受合成分子和内源性分子在明确的激动剂-拮抗剂中的调节 举止。可卡因是σ-1的激动剂，越来越多的证据表明可卡因激活了σ-1 促进σ1-Kv1.2蛋白复合体的形成，随后它们在血浆中积累 膜，从而降低NAcSh神经元的内在兴奋性。这种机制并不是 可卡因，并由包括甲基苯丙胺在内的其他精神刺激药物诱导，这表明常见的 导致精神刺激性上瘾的机制。我们之前的研究表明，无论是药理学上的 阻断或NAcSh特异性敲除σ1可阻止增强的Kv1.2电流和 降低兴奋性，同时减弱对可卡因的精神运动敏感性--这一过程可能有助于 成瘾的发展。此外，NAcSh特异性的Kv1.2亚基的过度表达，它模仿 可卡因诱导的神经元活动不足，放大了对可卡因的敏感度。我们假设 精神刺激性药物通过共同的DA非依赖途径发挥作用，导致σ1依赖 NAcSh MSN中Kv1.2的上调除了DA依赖的信号效应外，还促进成瘾。 在小鼠身上使用可卡因自我给药(SA)程序，这项研究将确定是否形成 σ1-Kv1.2蛋白复合体和放电率降低与可卡因渴求的孵化有关 在长期戒除可卡因SA之后(目标1)。这项研究还将采用：(I)组合 只有在细胞培养模型中才能使用的分子方法，包括多光子共聚焦细胞成像 Kv1.2体外可卡因暴露后的贩运，以及(2)针对KEY的药理学方法 在NAcSh切片中验证类似方法的内吞/循环机制(目标2)。以提供行为上的 与这一新的可卡因作用机制相关，我们将确定NAcSh特异性σ1和Kv1.2是如何 可卡因SA期间的调节改变了成瘾周期的后续阶段，包括在 退出(目标3)。我们的工作将对这一机制进行多管齐下的功能研究 从细胞内信号到细胞激发，以及成瘾行为的相关措施。这些 研究可能为对抗精神刺激性滥用的新的和补充的药物疗法铺平道路。

Drug addiction is a chronic psychiatric disorder that imposes a huge burden on the lives of addicted individuals, their families and society as a whole. Importantly, a significant proportion of addicts remain resistant to treatment. Diversifying pharmacotherapies that target mechanisms beyond canonical mechanisms of addiction involving dopamine (DA) and monoamine signaling could address this gap. Here we propose to study a novel and long-lasting neuroadaptation to chronic cocaine that is mediated by a non-canonical, DA-independent mechanism. Chronic cocaine induces a persistent decrease in the intrinsic excitability (firing rate) of nucleus accumbens shell (NAcSh) neurons. This adaptation is mediated by the sigma-1 protein (σ1; a.k.a. Sig-1R), a chaperone whose activity is regulated by synthetic and endogenous molecules in a clear agonist-antagonist manner. Cocaine is an agonist of σ1, and our accumulating evidence suggests that cocaine activation of σ1 enhances the formation of σ1-Kv1.2 protein complexes, their subsequent accumulation at the plasma membrane, thereby decreasing intrinsic excitability of NAcSh neurons. This mechanism is not unique to cocaine, and is induced by other psychostimulant drugs including methamphetamine, suggesting a common mechanism contributing to psychostimulant addiction. Our previous study showed that either pharmacological blockade or NAcSh-specific knockdown of σ1 prevents the development of enhanced Kv1.2 currents and reduced excitability while attenuating psychomotor sensitization to cocaine—a process that may contribute to the development of addiction. Moreover, NAcSh-specific overexpression of Kv1.2 subunits, which mimics cocaine-induced neuronal hypoactivity, amplifies sensitization to cocaine. We hypothesize that psychostimulant drugs act through a common DA-independent pathway that leads to σ1-dependent upregulation of Kv1.2 in NAcSh MSNs to promote addiction, in addition to DA-dependent signaling effects. Using cocaine self-administration (SA) procedures in mice, this research will determine whether the formation of σ1-Kv1.2 protein complexes and firing rate depression is associated with the incubation of cocaine craving after prolonged abstinence from cocaine SA (Aim 1). This research also will employ: (i) a combination of molecular approaches only available in cell culture models including multiphoton confocal cell imaging to track Kv1.2 trafficking following in vitro cocaine exposure, and (ii) a pharmacological approach targeting key endocytic/recycling machinery to validate a similar approach in NAcSh slices (Aim 2). To provide behavioral relevance to this novel mechanism of cocaine action, we will determine how NAcSh-specific σ1 and Kv1.2 modulations during cocaine SA alter subsequent stages of the addiction cycle, including drug seeking after withdrawal (Aim 3). Together, our work will provide a multipronged functional investigation of this mechanism of drug addiction, from intracellular signaling to cell firing and relevant measures of addictive behavior. These studies could pave the way for new and complementary pharmacotherapies to combat psychostimulant abuse.