Nicotinic Acetylcholine Receptor Mediated Bitter Taste Transduction

描述（由申请人提供）：每年有超过500万人主要死于与吸烟有关的肺癌。烟草含有尼古丁，这是导致强烈烟瘾的主要化合物。尼古丁通过尼古丁乙酰胆碱受体（nAChRs）介导中枢神经系统的作用而具有成瘾性。味觉受体基因（T2R38）的多态性使人能够感知苯硫胺的苦味，从而防止吸烟成瘾，减少吸烟的正强化作用。这表明味觉的变化在吸烟的背景下起着重要的作用，并提供了与尼古丁成瘾有关的重要线索。虽然尼古丁被描述为苦味，但编码尼古丁味道的分子和细胞机制尚不清楚。我们的研究表明，尼古丁通过两种平行的受体介导途径激活味觉系统。一种途径涉及g蛋白偶联受体（T2R）和下游效应器（g蛋白gustducin，酶PLC - 2和阳离子通道TRPM5），它们在甜、苦和鲜味苦味感知中很常见。第二种途径利用nachr，对尼古丁、乙酰胆碱、乙醇和其他苦味物质有反应，对它们的完整感官表征至关重要。本研究的总体目的是增加我们对不同nAChR亚基对尼古丁、乙酰胆碱、乙醇和其他苦味化合物苦味的贡献的理解。研究旨在利用分子技术（RT-PCR，定量rt - pct，免疫组织化学和原位杂交）研究味蕾细胞中不同nAChR亚基的存在。为了研究nAChRs在外周味觉转导中的作用，我们将在几种动物模型中使用全细胞膜片钳技术监测nAChRs的药理激动剂和拮抗剂对单个分离的味觉细胞的影响、中耳索味觉神经反应和舔舐率（尼古丁、乙酰胆碱、乙醇和其他苦味剂改变行为反应的衡量标准）的影响。具体来说，我们将使用特定的nAChR亚基基因或TRPM5阳离子通道基因被删除的转基因小鼠。本研究获得的nachr依赖的苦味感知途径的信息可能为我们提供有关味觉相关事件的信息，这些事件可能涉及尼古丁和酒精成瘾或预测因素。吸烟对食物消费和味觉偏好的影响可能是由于长期暴露于尼古丁对味蕾中nachr的影响而引起的外周味觉调节。

DESCRIPTION (provided by applicant): Every year, more than 5 million people die primarily from developing smoking related lung cancer. Tobacco contains nicotine, the major compound responsible for driving the strong addiction to smoking. Nicotine is addictive because of its effects on the central nervous system mediated by nicotinic acetylcholine receptors (nAChRs). The ability to sense the bitter taste of phenylthiocarbamide due to polymorphisms in a taste receptor gene (T2R38) protects a subject from developing a cigarette smoking addiction and reduces the positive reinforcement from smoking. This suggests that changes in taste play a significant role in the context of cigarette smoking and provide important cues involved in nicotine addiction. Although nicotine is described as bitter tasting, the molecular and cellular mechanisms that encode the taste of nicotine remain unclear. Our studies show that nicotine activates the taste system via two parallel receptor-mediated pathways. One pathway involves a G-protein coupled receptor (T2R) and down stream effectors (a G-protein gustducin, an enzyme PLC�2 and a cation channel, TRPM5) that are common to sweet, bitter and umami bitter sensing. The second pathway utilizes nAChRs and responds to nicotine, acetylcholine, ethanol and perhaps other bitter tastants and is essential for their complete sensory representation. The overall aim of this study is to increase our understanding of the contribution of different nAChR subunits to the bitter taste of nicotine, acetylcholine, ethanol and other bitter compounds. Studies are designed to investigate the presence of different nAChR subunits in taste bud cells using molecular techniques (RT-PCR, quantitative-RT-PCT, immunohistochemical and in situ hybridization). To investigate the role of nAChRs in peripheral taste transduction we will monitor the effects of pharmacological agonists and antagonists of nAChRs on single isolated taste cells using whole cell patch clamp technique, chorda tympani taste nerve responses and on lick rates as a measure of altered behavioral responses to nicotine, acetylcholine, ethanol and other bitter tastants in several animal models. Specifically, we will use genetically modified mice in which specific nAChR subunit genes or genes for TRPM5 cation channel have been deleted. The information obtained in this study on the nAChR-dependent bitter- sensing pathway may provide us with information regarding taste-related events that may be either involved in or predictors of nicotine and alcohol addiction. The effects of cigarette smoking on food consumption and taste preferences may occur from peripheral taste modulation due to chronic exposure to nicotine acting on nAChRs in taste buds among other factors.