Chronic Nicotine Effects on Receptor Subtypes

描述(申请人提供)：尼古丁的中枢神经系统作用是由多亚型神经性尼古丁胆碱能受体(NAChRs)介导的。尼古丁长期给药后的效果与急性给药后的效果不同，而且尼古丁的效果在不同的发育阶段也不同。我们以前的工作描述了慢性尼古丁对不同亚型nAChRs表达和功能的影响。了解这些受体在尼古丁使用过程中的变化表达模式对于理解胆碱能神经生理学以及尼古丁药理学至关重要。慢性尼古丁与依赖、基因表达和行为的变化以及神经发育的改变有关。考虑到在神经发育的关键时期，特别是由于吸烟或使用NRT产品的母亲以及开始尝试吸烟的青少年的产前暴露，尼古丁的广泛暴露，后一种影响至关重要。产前尼古丁暴露会对后代的后续发育和行为产生深远的影响。青少年接触尼古丁与成人对尼古丁和其他滥用药物的依赖率较高有关。因此，这两个时期是尼古丁暴露的唯一脆弱时期。本提案的首要目标是比较在三个关键年龄长期接触尼古丁的影响：产前、青春期和成年。我们将使用大鼠模型来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影响；我们将重点研究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。这些研究将检验尼古丁对这些参数的影响在暴露的不同发育阶段有所不同这一普遍假设。特别是，目标4将检验这样一种假设，即产前接触尼古丁会抑制青少年对随后的尼古丁挑战的反应，从而增加吸烟的数量，从而增加随后依赖的可能性。对于以下每个特定目标，我们将测试长期尼古丁暴露对nAChR亚型的表达(使用放射自显影和免疫沉淀)和功能(使用Rb外流和神经递质释放)、神经元形态的变化(测量树突长度和棘突密度)以及与尼古丁依赖相关的脑区整体基因表达的变化(使用微阵列和RTPCR)的短期和持久影响。不同的发展效果将通过不同目标的比较来确定。具体目标1.确定产前慢性尼古丁暴露的直接和持久的直接影响。2.确定青少年长期接触尼古丁的直接和持久影响。3.确定成人尼古丁暴露的直接和持久影响。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来确定产前尼古丁暴露的持续间接影响与公共卫生相关：这项工作将解决对理解长期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的关键假说，例如吸烟者和NRT使用者。这项工作将测量尼古丁对出生前暴露在老鼠体内的这些参数的影响，并将它们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在这些较年轻的年龄易受尼古丁影响的独特的特定年龄影响。

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.