AMPHETAMINE, INSULIN AND THE DA TRANSPORTER IN VIVO

描述(申请人提供)：滥用药物是一种普遍存在的精神疾病，对公众健康有极大的负面影响。因此，了解其神经基础是密集研究的重点。多巴胺(DA)转运体(DAT)是安非他明等滥用药物的主要作用部位，通过高亲和力将DA转运到终末，在调节DA神经传递中起关键作用。因此，了解DAT是如何被监管的，对研究苯丙胺滥用至关重要。在这方面，有越来越多的证据表明，胰岛素可以对DAT活性产生深刻的调控。例如，众所周知，食物限制和实验诱导的糖尿病都对苯丙胺的行为反应有重大影响。饮食失调和药物滥用并存的高发病率突显了这些观察的重要性。最近有报道称，低胰岛素血症大鼠的多巴胺摄取率降低，脑室注射胰岛素后，大鼠或稳定表达DAT的细胞对DA的摄取增加。重要的是，胰岛素似乎可以干扰苯丙胺在DAT的作用，并可以阻止苯丙胺诱导的DAT内化。对本提议特别重要的是，有苯丙胺自我给药史的糖尿病大鼠表现出增加而不是减少的DA摄取。因此，胰岛素及其信号通路可能成为开发药物滥用新疗法的新靶点。到目前为止，还没有研究评估胰岛素在体内控制DAT活性的作用。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，在体内测量胰岛素依赖的DA外流和清除的变化。由于胰岛素细胞作用的一个主要信号机制是刺激磷脂酰肌醇(PI)-3激酶，这些研究还将检验这样的假设，即当PI-3激酶被激活和抑制时，DA的外流和清除将分别增加和减少。重要的是，这些研究将确定苯丙胺的作用与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，苯丙胺的DA外流和清除的动力学以及运动刺激作用将与胰岛素状态密切相关。将胰岛素恢复到正常水平将恢复正常反应。这些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赏和动机的神经回路，以及为更大范围的RO1应用提供一个框架。反过来，这些研究可能有助于阐明饮食失调和药物滥用高发病率背后的神经机制。

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.