Transmission of Taste Signals in Taste Buds

味觉感受器细胞将化学信号转化为神经信息传递给味觉神经 支配味蕾的纤维。这项建议描述了旨在测试假设的实验，该假设在 味觉细胞对刺激的反应是释放ATP，然后激活离子型嘌呤能受体(P2X2 和P2X3)分布在味觉神经纤维上。以前的研究已经证明了这两个因素的存在。 味觉纤维上的受体。我们的初步数据显示，P2X2/P2X3中的味觉神经 双基因敲除小鼠对口腔中的任何味精都没有反应，尽管神经给出了 对触摸或热刺激的强大反应。同样，P2X2/3KO小鼠对 许多调味剂，包括甜味剂和许多苦味物质，尽管它们对 柠檬酸和其他苦味物质。这种响应性与上级的反应相匹配 支配喉部非味蕾化学感受器的喉神经。拟议中的实验 主要有三个目的：第一，测试P2X受体是否对味觉信息的传递是必需的。为 这些研究我们将从行为和电生理方面对系统进行表征，以测试 语言味觉系统的功能。我们还将测试喉部化学接收是否解释了 这些KO小鼠的剩余行为能力。第二，我们将利用解剖学和生理学 测试基因敲除小鼠的味蕾在结构和功能上是否正常的措施。 我们将评估P2X2/3KO小鼠味蕾的结构和功能，以测试受体细胞是否 正常，受体上皮细胞没有明显变化可能是导致味觉功能丧失的原因 P2X2/3KO小鼠。在最终目标中，我们将测试野生型和基因敲除小鼠的味蕾是否会释放 刺激时的三磷酸腺苷。这些功能研究将在体外通过使用荧光素- 荧光素酶检测和对ATP敏感的生物探针(所谓的“嗅探细胞”)。此外，我们还将利用 奎纳克林负荷量评估味觉细胞囊泡对三磷酸腺苷的摄取和释放。总而言之， 拟议的研究将测试ATP和离子型嘌呤能受体在味觉传递中的作用 信息。

Taste receptor cells transduce chemical signals into a neural message transmitted to the gustatory nerve fibers that innervate taste buds. This proposal describes experiments designed to test the hypothesis that in response to stimulation, taste cells release ATP which then activates ionotropic purinergic receptors (P2X2 and P2X3) on the gustatory nerve fibers. Previous studies have demonstrated the presence of these two receptors on intragemmal gustatory fibers. Our preliminary data show that gustatory nerves in P2X2/P2X3 double-knockout mice do not respond to any tastants applied to the oral cavity although the nerves give robust responses to touch or thermal stimuli. Similarly, the P2X2/3 KO mice do not respond behaviorally to many tastants including sweeteners, and many bitter substances although they do respond aversively to citric acid and other bitter substances. This spectrum of responsiveness matches that of the superior laryngeal nerve which innervates non-taste bud chemoreceptors on the larynx. The proposed experiments fall into 3 aims: first to test whether P2X receptors are necessary for transmission of taste information. For these studies we will characterize the system behaviorally and electrophysiologically to test the extent of function of the lingual gustatory system. We will also test whether laryngeal chemoreception accounts for remaining behavioral capabilities of these KO mice. Second, we will utilize anatomical and physiological measures to test whether taste buds in the knockout mice are normal both in terms of structure and function. We will assess structure and function of taste buds in P2X2/3 KO mice to test whether the receptor cells are normal and that no overt changes in the receptor epithelium may underlie the loss of taste function in the P2X2/3 KO mice. In the final aim, we will test whether taste buds in both wildtype and knockout mice release ATP upon stimulation. These functional studies will be carried out in vitro both by using the luciferin- luciferase assay and by ATP-sensing biological probes (so-called "sniffer-cells"). In addition, we will utilize quinacrine loading to assess vesicular uptake and release of ATP by taste cells. Taken together, the proposed studies will test the role of ATP and ionotropic purinergic receptors in transmission of taste information.