Nicotine Effects on the Adrenal Medulla and Brain

描述（由申请方提供）：长期给予尼古丁可增加蓝斑（LC）神经元中的儿茶酚胺释放和生物合成。酪氨酸羟化酶（TH）的活性控制着儿茶酚胺的生物合成。在大鼠和小鼠中，每天重复注射尼古丁14天后，LC中TH基因表达上调。这种TH基因表达的上调和随之而来的LC神经元中去甲肾上腺素生物合成能力的增加可能是导致尼古丁身体依赖的许多变化之一。本提案中的实验旨在增加我们对这种上调机制的理解。本提案中的研究检验了以下总体假设：重复尼古丁注射（每天两次）导致LC神经元重复激活，从而导致神经末梢区域去甲肾上腺素（NE）释放重复增强。这些重复的反应导致特定基因表达的适应性变化，其中之一是TH。在LC中，TH是通过转录和转录后机制诱导的，以响应慢性尼古丁。本研究的重点是转录后机制的研究。具体目标是：（1）测试响应于慢性尼古丁处理的LC中TH mRNA的诱导是否由增加的TH mRNA稳定性或与TH RNA初级转录物到成熟TH mRNA同种型的更有效或替代加工偶联的持续转录响应介导。(2)检测LC TH阳性神经元中是否表达多聚C结合蛋白（PCBP）亚型，以及慢性尼古丁处理是否诱导PCBP。(3)检测PCBP及其在TH mRNA的3' UTR中结合的富含polyC的序列是否参与TH mRNA的稳定，以响应介导尼古丁应答的信号传导途径的激活。

DESCRIPTION (provided by applicant): Chronic nicotine administration increases catecholamine release and biosynthesis in locus coeruleus (LC) neurons. Catecholamine biosynthesis is controlled by the activity of tyrosine hydroxylase (TH). In rats and mice, TH gene expression is up-regulated in the LC after daily repeated injections of nicotine for 14 days. This up-regulation of TH gene expression and the consequent increase in norepinephrine biosynthetic capacity in LC neurons may be one of the many changes that lead to physical dependence to nicotine. The experiments in this proposal are aimed at increasing our understanding of the mechanisms responsible for this up-regulation. The studies in this proposal test the following overall hypothesis: Repeated nicotine injections (twice per day) result in the repeated activation of LC neurons and consequent repeated enhanced release of norepinephrine (NE) in nerve terminal regions. These repeated responses lead to adaptive changes in the expression of specific genes, one of which is TH. In the LC, TH is induced via both transcriptional and post-transcriptional mechanisms in response to chronic nicotine. This proposal focuses on studying the post-transcriptional mechanisms. The specific aims are: (1) To test whether the induction of TH mRNA in the LC in response to chronic nicotine treatment is mediated by increased TH mRNA stability or a sustained transcriptional response coupled to more efficient or alternative processing of TH RNA primary transcripts to the mature TH mRNA isoform(s). (2) To test whether polyC-binding protein (PCBP) isoforms are expressed in TH-positive neurons in the LC and whether chronic nicotine treatment induces PCBP. (3) To test whether PCBP and the polyC-rich sequence to which it binds in the 3' UTR of TH mRNA participate in the stabilization of TH mRNA in response to the activation of signaling pathways that mediate the response to nicotine.