Nicotinic Signaling in the Brain

描述(申请人提供)：尼古丁是一种在这个社会被广泛滥用的药物，花费了数百万美元的医疗保健费用。显然，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。众所周知，尼古丁的作用是通过其激活烟碱型乙酰胆碱受体(NAChRs)的能力来实现的。在这项提议中，我们问的是nAChRs在大脑中的生理功能是什么。激活nAChRs的一个效果是它们增加了大脑中神经递质的释放，可能促进了突触的可塑性。这种作用通常是由nAChRs的一个子集介导的，一个包含Alpha7亚单位(A7-nAChRs)的子集，这个子集在提高细胞内钙水平和介导大脑中的钙依赖信号转导方面非常有效。在这项建议中，我们研究了这些受体在海马区苔藓纤维-CA3突触介导的谷氨酸释放增加的机制。在之前的资金支持期间，我们发现激活nAChR导致依赖于内质网储存钙的微小兴奋性突触后电流(MEPSCs)的频率和幅度显着增加。在这个方案中，我们使用荧光显微镜研究苔藓纤维末端是否存在内质网钙储存库，以及它们的性质。然后，我们问nAChR调节释放的机制是否特定于mEPSCs，或者它们是否也可以影响这些突触的诱发释放。我们还将研究使用苯乙酰染料和光转化的nAChRs动员的囊泡的性质和数量，然后用电子显微镜观察。这些研究将得出在我们实验室发现的一种新的可塑性形式的机制细节。最后，我们使用相关剂量的尼古丁和一个新开发的转基因小鼠模型来研究这种影响的生物学意义，其中胆碱能纤维被GFP-tau标记。这些研究将为开发抗击尼古丁成瘾的药理工具和治疗策略奠定基础，这些工具和治疗策略是基于受体生理学的现实模型。与公共健康相关：尼古丁的滥用耗费了我们社会数百万美元的医疗费用，以对抗由此导致的心脏病、癌症和其他令人衰弱的疾病。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器。我们的研究将为开发有效的抗击尼古丁成瘾的药物奠定基础，该药物将考虑尼古丁对大脑的全部影响，而这是目前严重缺乏的方法。

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.