Role of alpha3-containing nicotinic receptors in mediating central nicotine effec

描述（由申请方提供）：本提案的长期目标是了解尼古丁成瘾特性的分子和细胞基础，并阐明神经元烟碱乙酰胆碱受体（nAChR）在尼古丁的许多中枢介导的行为和生理效应中的功能作用。该建议的重点是α 3-亚单位含有nAChRs，发现在内侧缰高密度，也有牵连的腹侧被盖区（VTA），一个公认的组成部分的奖励途径。内侧缰核是一个进化上保守的大脑区域，已被证明对尼古丁的神经毒性作用非常敏感。此外，有人认为，精神分裂症中出现的一些认知缺陷可能与内侧缰核的潜在病理学有关。在这项研究中使用的主要工具是一种新的基因敲入小鼠，其中烟碱α 3亚基已被替换为含有5个氨基酸取代，赋予敏感性的药理学封锁α-银环蛇毒素（Bgtx）。这种敲入小鼠使得能够使用经典的药理学拮抗剂Bgtx来探测内侧缰核和腹侧被盖区中含有α 3的nAChR的功能和行为作用。首先，重要的是要确认Bgtx敏感的、含α 3的神经元nAChR在从靶向α 3/α 1 [5]突变（+/tm1.1）杂合子小鼠分离的脑冷冻切片中的区域表达。放射性Bgtx结合位点的放射自显影将用于此目的。在立体定位颅骨插管后，将Bgtx显微注射到（+/tm1.1）小鼠的内侧缰核和VTA中，以确定药理学阻断含NACh的nAChR对三种尼古丁相关行为的影响。其中包括：1）急性、低剂量全身性尼古丁的运动功能减退效应; 2）尼古丁的诱发口服偏好; 3）尼古丁诱导的癫痫发作。相关性：尼古丁是一种极易上瘾的药物，在西方世界，可预防的死亡率高达20%。尼古丁还能显著增强认知能力，某些遗传性癫痫与尼古丁受体有关。此外，胆碱能神经元的丧失与阿尔茨海默病有关，阿尔茨海默病是一种目前缺乏有效治疗的疾病。因此，了解尼古丁与其在中枢神经系统中的受体的分子相互作用对人类健康具有重大的潜在益处。

DESCRIPTION (provided by applicant): The long-term goals of this proposal are to understand the molecular and cellular basis for nicotine's addictive properties and to elucidate the functional role of neuronal nicotinic acetylcholine receptors (nAChRs) in the many centrally mediated behavioral and physiological effects of nicotine. This proposal focuses on alpha3-subunit-containing nAChRs which are found at high density in the medial habenula and which also have been implicated in the ventral tegmental area (VTA), a well recognized component of the reward pathway. The medial habenula is an evolutionarily conserved brain region that has been shown to be very sensitive to the neurotoxic effects of nicotine. Furthermore, it has been suggested that some of the cognitive deficits seen in schizophrenia may be linked to underlying pathology in the medial habenula. The main tool to be utilized in this study is a novel knock-in mouse in which the nicotinic alpha3-subunit has been replaced with one containing five amino acid substitutions that impart sensitivity to pharmacological blockade by alpha-bungarotoxin (Bgtx). This knock-in mouse enables the use of the classic pharmacological antagonist, Bgtx, to probe the functional and behavioral role of alpha3-containing nAChRs in the medial habenula and VTA. First, it will be important to confirm the regional expression of Bgtx-sensitive, alpha3- containing neuronal nAChRs in frozen sections of brains isolated from mice heterozygous for the targeted alpha3/alpha1[5] mutation (+/tm1.1). Autoradiography of radioactive-Bgtx binding sites will be used for this purpose. Following stereotaxic cranial cannulation, Bgtx will be microinjected into the medial habenula and VTA of (+/tm1.1) mice to determine the effect of pharmacological blockade of alphas-containing nAChRs on three nicotine-associated behaviors. These include: 1) the hypolocomotor effect of acute, low-dose systemic nicotine; 2) entrained oral preference for nicotine; and 3) nicotine-induced seizures. Relevance: Nicotine is an extremely addictive drug responsible for up to 20% of all preventable mortality in the western world. Nicotine also significantly enhances cognitive performance, and some inherited forms of epilepsy involve nicotinic receptors. In addition, a loss of cholinergic neurons is implicated in Alzheimer's disease, a disorder currently lacking effective treatment. Understanding the molecular interactions of nicotine with its receptors in the central nervous system therefore has significant potential to benefit human health.