Nicotinic acetylcholine receptor function in the mesolimbic dopamine system

描述（由申请人提供）：烟草成瘾是对美国和国外公众健康的严重威胁，开发新的治疗方法是一个主要的优先事项。尼古丁，香烟烟雾中主要的精神活性化合物，激活和/或使整个大脑的尼古丁乙酰胆碱受体（nachr）脱敏。在啮齿动物模型中，中边缘多巴胺（DA）通路中的nachr对尼古丁的奖励和强化特性至关重要，这表明它们可能是尼古丁在人类中作用的关键介质。虽然已知alpha4和alpha6 nAChR亚基是中脑边缘DA通路nAChR的重要组成部分，但该通路中足够和/或必要的nAChR的精确组成和/或化学计量尚不清楚。此外，人们对尼古丁暴露后大脑中产生奖励行为的变化知之甚少。这一提议将验证这样的假设，即在中脑边缘DA通路中激活alpha4alpha6beta2*（*表示nAChR五聚体中可能存在其他亚基）nAChRs足以产生尼古丁的奖励效应。证实或反驳这一假设将导致进一步确定相关的nAChR亚型

DESCRIPTION (provided by applicant): Tobacco addiction is a serious threat to public health in the United States and abroad, and development of new therapeutic approaches is a major priority. Nicotine, the primary psychoactive compound in cigarette smoke, activates and/or desensitizes nicotinic acetylcholine receptors (nAChRs) throughout the brain. nAChRs in the mesolimbic dopamine (DA) pathway are crucial for the rewarding and reinforcing properties of nicotine in rodent models, suggesting that they may be key mediators of nicotine's action in humans. Although it is known that alpha4 and alpha6 nAChR subunits are important components of mesolimbic DA pathway nAChRs, the precise composition and/or stoichiometry of nAChRs in this pathway that are sufficient and/or necessary for nicotine reward remains unknown. Furthermore, the changes in the brain following nicotine exposure that give rise to reward behavior are poorly understood. This proposal will test the hypothesis that activation of alpha4alpha6beta2* (*denotes that other subunits may be present in the nAChR pentamer) nAChRs in the mesolimbic DA pathway is sufficient for nicotine's rewarding effects. Confirming or refuting this hypothesis will result in further identification of the relevant nAChR subtypes in the mesolimbic DA pathway that mediate nicotine's biophysical and/or behavioral effects. Using a combination of behavioral, electrophysiological, and biochemical techniques, we will address our hypothesis with three specific aims. In Specific Aim 1, we will test the idea that activation o alpha4alpha6beta2* nAChRs is sufficient for nicotine reward-like behavior. Using mice which express alpha6* nAChRs that are hypersensitive to nicotine, in parallel with a compound with modest functional selectivity for α6α2* nAChRs, we will determine whether selective activation of these receptors is sufficient for nicotine CPP. In Specific Aim 2, we will use patch clamp electrophysiology to test the hypothesis that stimulation of alpha4alpha6beta2* nAChRs is sufficient to activate ventral tegmental area (VTA) DA neurons and strengthen glutamatergic input to these cells. In Specific Aim 3, we directly measure changes in nAChR and glutamatergic receptor function in DA neurons from animals exposed to nicotine. The proposed studies will enhance our understanding of the key nAChRs in the mesolimbic DA pathway that are involved in nicotine addiction. Identifying the nAChRs that are sufficient for nicotine reward should lead to a more rational and focused effort to develop new smoking cessation therapeutics.