Chronic Nicotine Effects on Receptor Subtypes

描述（由申请人提供）：尼古丁对中枢神经系统的影响是由神经元尼古丁胆碱能受体（nachr）的多个亚型介导的。慢性给药后尼古丁的作用与急性给药后不同，在不同的发育阶段尼古丁的作用也不同。我们之前的工作描述了慢性尼古丁对nachr不同亚型的表达和功能的影响。了解这些受体在尼古丁使用过程中的表达模式变化对于理解胆碱能神经生理学和尼古丁药理学至关重要。慢性尼古丁与依赖性、基因表达和行为的改变以及神经发育的改变有关。后一种影响是至关重要的，因为在关键的神经发育时期，尼古丁会广泛暴露于其中，特别是由于产前吸烟或使用NRT产品的母亲以及开始尝试吸烟的青少年暴露于尼古丁中。产前尼古丁暴露会对后代的发育和行为产生深远的影响。青少年对尼古丁的接触与成人对尼古丁和其他滥用药物的依赖率较高有关。因此，这段时间是尼古丁暴露的最脆弱时期。本提案的总体目标是比较慢性尼古丁暴露在三个关键年龄段的影响：产前、青春期和成年期。我们将采用大鼠模型研究慢性尼古丁暴露对nAChR表达和功能、神经元形态和基因表达的重叠效应；我们将重点关注与尼古丁依赖相关的受体、基因和大脑区域。特别是，我们将检查尼古丁暴露对这些参数的持续影响。这些研究将检验一个普遍的假设，即尼古丁对这些参数的影响在不同的发育阶段是不同的。特别地，Aim 4将检验产前尼古丁暴露抑制青少年对随后尼古丁挑战的反应的假设，增加吸烟的数量，从而增加随后依赖的可能性。对于以下每个特定目标，我们将测试慢性尼古丁暴露对nAChR亚型表达（使用放射自显影和免疫沉淀）和功能（使用铷外排和神经递质释放）的短期和持续影响，神经元形态的改变（测量树突长度和脊柱密度），以及与尼古丁依赖相关的大脑区域整体基因表达的变化（使用微阵列和rtPCR）。不同的发展效应将通过不同目标的比较来确定。1.具体目标确定产前慢性尼古丁暴露的即时和持续的直接影响。2. 确定青少年慢性尼古丁暴露的即时和持续的直接影响。3. 确定成人尼古丁暴露的即时和持续直接影响。4. 通过确定产前尼古丁暴露如何改变青少年对新的尼古丁暴露的反应能力，确定产前尼古丁暴露的持续间接影响公共卫生相关性：这项工作将解决对理解慢性尼古丁暴露如何改变受体表达和功能、神经元结构和基因表达至关重要的假设，例如发生在吸烟者和NRT使用者中。这项工作将测量尼古丁在大鼠产前暴露对这些参数的影响，并将其与青春期和成年期暴露的影响进行比较。这些研究应该有助于更好地理解这些年轻人对尼古丁影响的潜在脆弱性的独特年龄特异性影响。

DESCRIPTION (provided by applicant): The CNS effects of nicotine are mediated by multiple subtypes of neuronal nicotinic cholinergic receptors (nAChRs). The effects of nicotine after chronic administration differ from those after acute administration, and nicotine effects also vary at different stages of development. Our previous work characterized the effects of chronic nicotine on expression and function of different subtypes of nAChRs. Knowledge of the shifting expression pattern of these receptors during nicotine use is critical for understanding cholinergic neurophysiology as well as nicotine pharmacology. Chronic nicotine is associated with dependence, changes in gene expression and behavior, and altered neural development. This latter effect is of critical importance given the widespread exposure to nicotine that occurs during periods of critical neural development, particularly due to prenatal exposure from mothers who smoke or use NRT products, and adolescents who are beginning to experiment with tobacco. Prenatal nicotine exposure can have profound effects upon subsequent development and behavior of offspring. Adolescent exposure to nicotine is associated with higher rates of adult dependence, both to nicotine and to other drugs of abuse. Thus these represent uniquely vulnerable periods for nicotine exposure. The overarching goal of the present proposal is to compare the effects of chronic nicotine exposure at three critical ages: prenatal, adolescence and adult. We will employ rat models to study the overlapping effects of chronic nicotine exposure on nAChR expression and function, neuronal morphology and gene expression; we will focus on receptors, genes and brain regions associated with nicotine dependence. In particular, we will examine for persistent effects of nicotine exposure on these parameters. These studies will test the general hypothesis that nicotine's effects on these parameters differ at different developmental stages of exposure. In particular, Aim 4 will test the hypothesis that prenatal nicotine exposure inhibits the response of adolescents to subsequent nicotine challenge, increasing the number of cigarettes smoked and thus the likelihood of subsequent dependence. For each of the following Specific Aims, we will test for both the short-term and persistent effects of chronic nicotine exposure on expression (using autoradiography and immunoprecipitation) and function (using rubidium efflux and neurotransmitter release) of nAChR subtypes, alteration of neuronal morphology (measuring dendritic length and spine density), and changes in global gene expression (using microarrays and rtPCR) in brain regions associated with nicotine dependence. Differential developmental effects will be determined by comparison across aims. SPECIFIC AIMS 1. Determine the immediate and the persistent direct effects of prenatal chronic nicotine exposure. 2. Determine the immediate and the persistent direct effects of adolescent chronic nicotine exposure. 3. Determine the immediate and the persistent direct effects of adult nicotine exposure. 4. Determine the persistent indirect effects of prenatal nicotine exposure by determining how prenatal nicotine exposure alters the ability of the adolescent to respond to a new nicotine exposure PUBLIC HEALTH RELEVANCE: This work will address hypotheses critical for understanding how chronic exposure to nicotine, such as occurs in tobacco smokers and NRT users, can alter receptor expression and function, neuronal structure, and gene expression. The work will measure nicotine's effects on these parameters caused by prenatal exposure in rats, and compare them to those effects from exposure during adolescence and adulthood. These studies should help to better understand the unique age-specific effects underlying vulnerability to nicotine's effects at these younger ages.