Nicotinic Signaling in the Brain

描述（由申请人提供）：尼古丁是一种被广泛滥用的药物，在这个社会上花费了数百万美元的医疗保健费用。很明显，任何针对尼古丁成瘾的药理学方法的起点都必须从了解这种药物作用的机制细节开始。已知尼古丁的作用是通过其激活尼古丁乙酰胆碱受体（nAChRs）的能力来介导的。在这个提议中，我们询问nachr在大脑中的生理功能是什么。nachr激活的一个影响是，它们增加了大脑中的神经递质释放，可能促进了突触的可塑性。这种作用通常由一组nAChRs介导，其中一组含有α 7亚基（a7-nAChRs），该亚基在提高细胞内钙水平和介导脑内钙依赖性信号转导方面非常有效。在本研究中，我们研究了海马苔藓纤维- ca3突触中这些受体介导的谷氨酸释放增加的机制。在之前的资助期内，我们表明nAChR激活导致依赖内质网储存钙的微型兴奋性突触后电流（mEPSCs）的频率和幅度急剧增加。在这个提议中，我们研究是否有内质网钙储存在苔藓纤维终端和什么性质可能是使用荧光显微镜。然后，我们想知道nAChR调节释放的机制是否仅针对mepsc，或者它们是否也可以影响这些突触的诱发释放。我们还将使用苯乙烯染料和光电转化，然后用电子显微镜研究nAChRs动员的囊泡的性质和数量。这些研究将涉及我们实验室发现的一种新型可塑性的机制细节。最后，我们利用相关剂量的尼古丁和新开发的转基因小鼠模型研究了这种效应的生物学意义，其中胆碱能纤维被GFP-tau标记。这些研究将为对抗尼古丁成瘾的药理学工具和治疗策略的发展奠定基础，这些都是基于受体生理学的现实模型。与公共健康相关：滥用尼古丁使我们的社会在与由此引起的心脏病、癌症和其他使人衰弱的疾病作斗争方面花费了数百万美元的医疗费用。在这个项目中，我们通过检查尼古丁篡夺大脑中重要信号通路的能力，来研究尼古丁如何作为大脑功能的强大调节剂。我们的研究将为开发对抗尼古丁成瘾的有效药物奠定基础，这种药物将全面考虑尼古丁对大脑的影响，这是目前非常缺乏的一种方法。

DESCRIPTION (provided by applicant): Nicotine is a drug that is widely abused in this society costing millions of dollars in health care. It is clear that the starting point of any pharmacological approach to target nicotine addiction must begin with the understanding of the mechanistic details of the action of this drug. It is known that the actions of nicotine are mediated by its ability to activate nicotinic acetylcholine receptors (nAChRs). In this proposal we ask what physiological functions of nAChRs in the brain are. One effect of activation of nAChRs is that they increase neurotransmitter release in the brain, possibly facilitating synaptic plasticity. This effect is commonly mediated by a subset of nAChRs, one containing the alpha7 subunit (a7-nAChRs), a subset that is very effective at raising intracellular calcium levels and mediating calcium-dependent signal transduction in the brain. In this proposal we examine the mechanisms underlying increased glutamate release mediated by these receptors at the mossy fiber-CA3 synapses in the hippocampus. In the previous funding period we show that nAChR activation results in a dramatic increase in frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) dependent on ER store calcium. In this proposal we investigate whether there are ER calcium stores at the mossy fiber terminals and what their properties might be using fluorescence microscopy. We then ask whether the mechanisms underlying nAChR modulation of release are specific to mEPSCs or whether they can also influence evoked release at these synapses. We will also investigate the nature and population of vesicles that are mobilized by nAChRs using styryl dyes and photoconversion followed by electron microscopy. These studies will arrive at the mechanistic details of a novel form of plasticity discovered in our lab. Lastly, we investigate the biological significance of the effect using relevant doses of nicotine and a newly developed transgenic mouse model where cholinergic fibers are labeled with GFP-tau. These studies will set the stage for the development of pharmacological tools and therapeutic strategies to combat nicotine addiction, ones that are based on realistic models of receptor physiology. PUBLIC HEALTH RELEVANCE: The abuse of nicotine costs our society millions in health care costs to combat the resultant heart disease, cancer, and other debilitating illnesses. In this project we examine how nicotine acts as a powerful modulator of brain functions, by examining its ability to usurp important signaling pathways in the brain. Our studies will form the basis for developing effective drugs to combat nicotine addiction, one that will take into account the entirety of nicotine's effects on the brain, an approach sorely lacking at present.