Molecular Bases for Effects of Nicotine

描述（由申请人提供）：该项目的长期目标是确定慢性尼古丁暴露是否以及如何改变神经系统功能。该项目基于一个中心假设，即长期暴露于尼古丁会导致不同尼古丁乙酰胆碱受体（nAChR）亚型的数量和功能发生长期变化。这些影响可能与尼古丁依赖、烟草制品使用、烟草相关疾病、预防、限制或停止使用烟草的治疗以及神经和精神疾病的治疗有关。初步研究结果支持了我们的假设，即慢性尼古丁暴露会导致(i) nAChR功能的持续失活，以及（ii） nAChR数量的增加，这是通过两种因果和机械上不同的翻译后过程实现的。尼古丁作用的剂量和时间依赖性被认为是nAChR亚型特异性的，其他药物作用于改变nAChR数量和功能的药理学特征也是如此。这个多层次项目的一个主要目的是确定暴露于尼古丁或相关物质对不同人类nAChR亚型功能的影响。另一个主要目的是确定这些药物对nAChR数量的影响。为了这两个目的，研究将涉及通过模型细胞系自然和/或异源表达的α 1 β 1 γ δ -（肌肉型）、α 3 α 5 β 4-（自主神经）、α 4 β 2-（脑尼古丁结合）和α 7-（自主神经或脑神经毒素结合）nAChR。将确定尼古丁细胞治疗的时间（作用开始和恢复）和剂量依赖效应。使用其他药物单独使用或与尼古丁联合使用，也将获得时间和剂量谱，以评估它们是否模仿或阻断尼古丁的作用，nAChR的功能活性将通过电生理记录和离子通量测定来量化。放射配体结合和免疫测定将用于定量nAChR并评估其亚细胞分布和代谢。nAChR的化学反应性和突变研究将被用于确定尼古丁和其他药物作用的机制。

DESCRIPTION (provided by applicant): The long-term goal of this project is to establish whether and how chronic nicotine exposure alters nervous system function. The project is based on the central hypothesis that extended exposure to nicotine induces long-lasting changes in numbers and function of diverse nicotinic acetylcholine receptor (nAChR) subtypes. These effects have potential relevance for nicotine dependence, use of tobacco products, tobacco-related diseases, treatments to prevent, limit or cease tobacco use, and therapies for neurological and psychiatric disorders. Preliminary findings suggest our hypothesis that chronic nicotine exposure causes both (i) a persistent inactivation of nAChR function and (ii) an increase in numbers of nAChR via two causally- and mechanistically-distinct, posttranslational processes. Dose- and time-dependence of nicotine's effects are postulated to be nAChR subtype-specific, as are pharmacological profiles for other drugs acting to alter nAChR numbers and function. One principal aim of this multi-layered project is to establish effects of exposure to nicotine or related substances on function of diverse, human nAChR subtypes. The other principal aim is to determine effects of those agents on numbers of nAChR. For both aims, studies will involve alpha1 beta1 gamma delta- (muscle-type), (alpha3 alpha5 beta4- (autonomic), alpha4 beta2-(brain nicotine-binding), and alpha7- (autonomic or brain neurotoxin-binding) nAChR expressed naturally and/or heterologously by model cell lines. Time (onset of effects and recovery)- and dose-dependent effects of cell treatment with nicotine will be established. Time and dose profiles will also be obtained using other drugs alone or in combination with nicotine to assess whether they mimic or block nicotine's effects, nAChR functional activity will be quantified by electrophysiological recording and ion flux assays. Radioligand binding and immuno- assays will be used to quantitate nAChR and to assess their subcellular distribution and metabolism. Chemical reactivity of nAChR and mutational studies will be among those used to establish mechanisms involved in effects of nicotine and other drugs. These studies are significant because they will provide new perspectives on sites and mechanisms of chronic nicotine action in the modulation of nervous system function. Insights will also be provided into molecular bases of nicotine dependence. Specific nAChR subtypes that are affected most powerfully by chronic nicotine exposure will be identified. Insights will also be provided into the kinds of drugs that block or mimic nicotine's actions. Collectively, this knowledge will benefit development of strategies to treat mood, cognitive, and other nervous system disorders.