Genetics of Nicotine Tolerance: Role of Receptors

项目摘要/摘要 最近对几个人类群体的分析已经确定了一些与 与吸烟行为和与不同的nAChR亚基相对应的方面。这些研究强烈地 支持受体亚单位结构或表达的遗传差异影响烟草的观点 使用。然而，目前还没有确定哪种遗传差异是鼓励的，哪种是阻碍的。 烟草使用。动物长期接触尼古丁，或人类长期接触烟草，都会导致 宽容和依赖。尼古丁最初的作用部位是烟碱胆碱能受体。 (NAChR)，其固有神经递质是乙酰胆碱。中有许多不同类型的nAChR 大脑和外围设备。尼古丁与这些不同受体的相互作用不同，可能导致 对药物有不同的反应。众所周知，长期接触尼古丁也会改变这种数量， 也许还有一些烟碱型胆碱能受体(NAChR)的功能。然而，慢性尼古丁 暴露不会以相同的方式影响每个nAChR子类型。将以小鼠为模型生物 检查慢性尼古丁治疗的效果。尼古丁对小鼠的影响受基因和基因的影响 特定nAChR基因缺失(敲除)或突变(敲除)的小鼠已被 已生成。基因敲除小鼠和敲除小鼠将被用来研究一些行为变化。 尼古丁治疗，主要是耐受性。此外，慢性尼古丁治疗对患者的影响 将测量几种不同的nAChR亚型的表达和功能。有两个具体目标。 4？2*nAChR在调节对慢性尼古丁的反应中的作用将在目标1中进行研究。 NAChR是大脑中表达最高的亚型，长期尼古丁治疗会增加这种数量 这些受体中的一个。我们计划了四种类型的实验来详细研究这种响应：a)测量 基因敲除，即基因完全消失的地方；b)测量小鼠的反应，在小鼠中， ？2基因已部分缺失；c)测量表达突变的小鼠的反应，使这些突变 受体超敏；以及d)评估选择性与之相互作用的药物的治疗效果 2-nAChR。5和4亚基在调节对慢性尼古丁的反应中的作用是 在目标2中进行了研究。5很有趣，因为它是与nAChR基因最密切相关的 烟草使用，而？4是有趣的，因为nAChR结合了这个亚单位影响尼古丁戒断和 可能会削弱耐受性的发展。？5和？4突变和杂合子小鼠的反应将是 与野生型小鼠相比。这些研究的结果将为监管提供新的信息 主要的尼古丁受体亚型以及另外两种亚型对由 慢性尼古丁。研究结果还有助于确定特定的行为和生化反应 由基因介导的慢性尼古丁被认为是人类吸烟的重要因素。

Project Summary/Abstract Recent analyses of several human populations have identified a number of genetic markers which correlate with aspects of smoking behavior and that correspond to different nAChR subunits. These studies strongly support the contention that genetic differences in receptor subunit structure or expression influence tobacco use. However, it has not been established which of the genetic differences encourage and which discourage tobacco use. Chronic exposure of animals to nicotine, or of humans to tobacco, results in the development of tolerance and dependence. The initial sites of action of nicotine are the nicotinic cholinergic receptors (nAChR), for which the native neurotransmitter is acetylcholine. There are many different types of nAChR in the brain and in the periphery. Nicotine's interaction with these various receptors differs and can lead to different responses to the drug. It is well established that chronic nicotine exposure also changes the number, and perhaps the function, of some nicotinic cholinergic receptors (nAChR). However, chronic nicotine exposure does not affect each nAChR subtype in the same way. Mice will be used as the model organism to examine effects of chronic nicotine treatment. The effects of nicotine in mice are influenced by genotype and mice from which a specific nAChR gene has been deleted (knockout) or mutated (knockin) have been generated. The knockout and knockin mice will be used to investigate some behavioral changes induced by nicotine treatment, primarily tolerance. Furthermore, the effects of chronic nicotine treatment on the expression and function of several different nAChR subtypes will be measured. There are two specific aims. The role of ¿4¿2*nAChR in modulating response to chronic nicotine will be investigated in Aim 1. ¿4¿2*- nAChR is the most highly expressed subtype in the brain and chronic nicotine treatment increases the number of these receptors. We plan four types of experiments to study this response in detail a) measure effects in ¿4 knockouts, where the gene is completely gone; b) measure the response in mice in which either or both ¿4 and ¿2 genes have been partially deleted; c) measure response in mice expressing mutations that make these receptors hypersensitive; and d) evaluate the effects of treatment with a drug that interacts selectively with ¿4¿2-nAChR. The role of the ¿5 and ¿4 subunits in modulating responses to chronic nicotine will be investigated in Aim 2. ¿5 is interesting because it is the nAChR gene that most robustly correlates with tobacco use, while ¿4 is interesting because nAChR incorporating this subunit affect nicotine withdrawal and may diminish tolerance development. Response of ¿5 and ¿4 null mutant and heterozygote mice will be compared to that of wild-type mice. The results of these studies will provide new information on the regulation of the major nicotinic receptor subtype and the contribution of two other subtypes to changes induced by chronic nicotine. The results could also help identify specific behavioral and biochemical responses to chronic nicotine mediated by genes identified as important factors in human smoking.