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

描述（由申请人提供）：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，并阐明神经元尼古丁乙酰胆碱受体（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。本研究的重点是含有alpha3亚基的nachr，这些nachr在内侧束中高密度发现，也与腹侧被盖区（VTA）有关，后者是奖励通路的一个公认的组成部分。内侧束是一个进化上保守的大脑区域，对尼古丁的神经毒性作用非常敏感。此外，有研究表明，精神分裂症中的一些认知缺陷可能与内侧链的潜在病理有关。本研究中使用的主要工具是一种新型敲入小鼠，其中尼古丁α 3亚基被一个含有五个氨基酸取代的亚基所取代，从而对α -班加罗毒素（Bgtx）的药物阻断具有敏感性。这种敲入小鼠可以使用经典的药理学拮抗剂Bgtx来探测含有alpha3的nachr在内侧链和VTA中的功能和行为作用。首先，确认bgtx敏感、含有alpha3的神经元nAChRs在α 3/ α 1[5]突变（+/tm1.1）杂合小鼠脑冷冻切片中的区域表达是很重要的。放射性- bgtx结合位点的放射自显影将用于此目的。在立体定向颅骨插管后，将Bgtx微注射到（+/tm1.1）小鼠的内侧束和VTA，以确定药物阻断含α的nAChRs对三种尼古丁相关行为的影响。这包括：1)急性、低剂量全身性尼古丁的低运动效应；2)对尼古丁的口服偏好；3)尼古丁引起的癫痫。相关性：尼古丁是一种极易上瘾的药物，在西方世界，高达20%的可预防死亡是由尼古丁造成的。尼古丁还能显著提高认知能力，一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，这种疾病目前缺乏有效的治疗方法。因此，了解尼古丁与其中枢神经系统受体的分子相互作用对人类健康具有重要的潜在益处。

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.