Role of Brain Nicotinic Receptors in Addiction Behaviors

描述(申请人提供)：吸烟已导致肺癌和心脏病的流行，是美国健康状况不佳的主要可预防原因。这种流行是由于人们渴望感受尼古丁的影响，尼古丁很可能是通过尼古丁与神经元尼古丁乙酰胆碱受体(NAChRs)的结合而介导的。尼古丁依赖的机制尚不清楚，然而，我们已经发现了一个在大脑中表达的nAChRs大家族。具有α4和β2亚基的nAChRs对尼古丁的亲和力最高，在人类吸烟者和动物模型中，长期尼古丁暴露(吸烟)会导致这些nAChRs的增加或上调。我们认为，长期尼古丁暴露改变了脑内nAChRs的性质，这些变化是依赖的分子机制。最初接触尼古丁会激活nAChRs，但长期接触会抑制nAChR功能(脱敏)。代偿机制(上调)是由慢性尼古丁诱导的，潜在地维持正常的神经传递水平。通过戒烟去除激动剂可以恢复nAChRs，产生过量的活性nAChRs，这可能有助于生理上继续吸烟的愿望。为了验证这一假设，我们将使用组织培养模型系统和转基因小鼠系来研究尼古丁调节高亲和力α4/β2 nAChRs功能和表达的机制(S)。我们建议使用体外表达系统结合遗传和生化方法来研究nAChR上调的潜在分子机制(S)，以表征我们已经鉴定的几种与α4/β2 nAChRs相互作用的蛋白质。我们还将探讨nAChR脱敏在诱导上调中的作用及其对尼古丁成瘾相关行为的影响，方法是利用在alpha4和beta2亚基中发现的几个突变的影响，这些突变对受体脱敏具有不同的影响，因此可能会以不同的方式改变受体的上调。

DESCRIPTION (provided by applicant): Cigarette use has led to an epidemic of lung cancer and heart disease and is the major preventable cause of poor health in the U.S. This epidemic is driven by the desire to feel the effects of nicotine, which are likely mediated by binding of nicotine to neuronal nicotinic acetylcholine receptors (nAChRs). The mechanisms of nicotine dependence are unknown, however, we have discovered a large family of nAChRs expressed in brain. nAChRs with alpha4 and beta2 subunits have the highest affinity for nicotine and chronic nicotine exposure (smoking) produces an increase, or up-regulation, of these nAChRs in human smokers and animal models. We proposed that long term nicotine exposure changes the properties of nAChRs in brain, and these changes underlie the molecular mechanism of dependence. Initial exposure to nicotine activates nAChRs, but chronic exposure depresses nAChR function (desensitization). Compensatory mechanisms (up-regulation) are induced by chronic nicotine, potentially to maintain normal levels of neurotransmission. Removal of agonist via smoking cessation allows recovery of nAChRs, producing an excess of active nAChRs which may contribute to the physiological desire to continue smoking. To test this hypothesis we will examine the mechanism(s) by which nicotine regulates the function and expression of the high affinity alpha4/beta2 nAChRs using tissue culture model systems and lines of genetically altered mice. We propose to investigate the underlying molecular mechanism(s) of nAChR up-regulation using an in vitro expression system in combination with genetic and biochemical methods to characterize several proteins that we have identified that interact with alpha4/beta2 nAChRs. We will also explore the role of nAChR desensitization in the induction of up-regulation and its effects on behaviors related to nicotine addiction by capitalizing on the effects of several mutations identified in alpha4 and beta2 subunits which have contrasting effects on receptor desensitization and may therefore alter receptor up-regulation differently