AMPHETAMINE, INSULIN AND THE DA TRANSPORTER IN VIVO

描述（由申请人提供）：药物滥用是一种普遍存在的精神疾病，具有巨大的负面公共卫生后果。因此，了解其神经基础是密集研究的焦点。多巴胺（DA）转运蛋白（DAT）是滥用药物（如安非他明）的主要作用位点，并通过高亲和力转运DA进入末端来调节DA神经传递。因此，了解DAT是如何调节的，对安非他明滥用的研究至关重要。在这方面，有一致的证据表明，胰岛素可以产生深刻的调节控制DAT活动。例如，已知食物限制以及实验诱导的糖尿病对安非他明的行为反应有重大影响。饮食失调和药物滥用的高并发症突出了这些观察结果的重要性。最近，据报道，DA摄取率降低hypoinsulinemic大鼠和胰岛素脑室内应用于大鼠或细胞稳定转染的DAT增加DA摄取。重要的是，似乎胰岛素可以干扰安非他明在DAT的作用，并可以防止安非他明诱导的DAT的内化。特别重要的是，本建议的糖尿病大鼠与安非他明自我管理的历史显示增加，而不是减少DA摄取。因此，胰岛素及其信号通路可能是开发药物滥用新疗法的新靶点。迄今为止，没有研究评估胰岛素在体内控制DAT活性中的作用。由于胰岛素在促进药物滥用潜力方面的潜在影响，拟议的研究将使用一种创新的方法，高速计时电流法，来测量体内DA流出和清除的胰岛素依赖性变化。由于胰岛素细胞作用的主要信号传导机制是磷脂酰肌醇（PI）-3激酶的刺激，因此这些研究还将检验以下假设：在PI-3激酶激活和抑制后，DA流出和清除将分别增加和减少。重要的是，这些研究将确定安非他明的作用和胰岛素状态之间的关系，因为它们与DAT活性有关。我们的一般假设是，动力学的DA流出和清除，以及运动刺激作用的安非他明将密切相关的胰岛素状态。胰岛素恢复到正常水平将恢复正常反应。这里获得的结果不仅将提高我们对DAT调节的基本理解，而且重要的是控制奖励和动机的神经回路，以及为更大的RO1应用提供框架。反过来，这些研究可能有助于阐明饮食失调和药物滥用的高并发症背后的神经机制。

DESCRIPTION (provided by applicant): Drug abuse is a prevalent psychiatric disorder with immense negative public health consequences. As a result, understanding its neural underpinnings is a focus of intense research. The dopamine (DA) transporter (DAT) is a primary site of action of drugs of abuse such as amphetamine and is critical in regulating DA neurotransmission by high affinity transport of DA into the terminal. Understanding how the DAT is regulated is therefore of fundamental importance to studies of amphetamine abuse. In this regard, there is converging evidence that insulin can produce profound regulatory control of DAT activity. It is known for example that both food restriction as well as experimentally-induced diabetes have major effects on behavioral responses to amphetamine. The significance of these observations is underlined by the high co-morbidity of eating disorders and drug abuse. Recently it has been reported that rates of DA uptake are decreased in hypoinsulinemic rats and that insulin applied intracerebroventricularly to rats or to cells stably transfected with the DAT increases DA uptake. Importantly, it seems that insulin can interfere with the action of amphetamine at the DAT and can prevent amphetamine-induced internalization of the DAT. Of particular importance to the present proposal is that diabetic rats with a history of amphetamine self-administration show increased rather than decreased DA uptake. Insulin and its signaling pathways may therefore represent a novel target for the development of new treatments for drug abuse. To date no studies have assessed the role of insulin in controlling DAT activity in vivo. Because of the potential impact of insulin in promoting the abuse potential of drugs the proposed study will use an innovative approach, high-speed chronoamperometry, to measure insulin-dependent changes in DA efflux and clearance in vivo. Because a major signaling mechanism that underlies insulin's cellular actions is stimulation of phosphatidylinositol (PI)-3 kinase these studies will also test the hypothesis that DA effiux and clearance will be increased and decreased respectively, upon activation and inhibition of PI-3 kinase. Importantly, these studies will determine the relationship between the action of amphetamine and insulin status as they relate to DAT activity. Our general hypothesis is that the kinetics of DA efflux and clearance as well the locomotor stimulatory effects of amphetamine will be tightly correlated with insulin status. Restoration of insulin to normal levels will restore normal responses. The results obtained here will not only improve our fundamental understanding of DAT regulation but importantly the neural circuitry controlling reward and motivation, as well as provide a framework for a larger RO1 application. In turn, these studies may help to illuminate the neural mechanisms underlying the high co-morbidity of eating disorders and drug abuse.