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 味蕾神经纤维该提案描述了旨在测试以下假设的实验： 响应刺激，味细胞释放ATP，然后激活离子型嘌呤能受体（P2 X2 和P2 X3）在味觉神经纤维上的作用。以前的研究已经证明了这两种物质的存在 感受器位于胚内味觉纤维上。我们的初步数据表明，P2 X2/P2 X3中的味觉神经 双基因敲除小鼠对施加到口腔的任何促味剂都没有反应， 对触摸或热刺激的强烈反应。类似地，P2 X2/3 KO小鼠不对以下行为作出反应： 包括甜味剂在内的许多促味剂，以及许多苦味物质，尽管它们确实对 柠檬酸和其他苦味物质。这种反应范围与上级的反应范围相匹配 喉神经，其支配喉上的非味蕾化学感受器。拟议的实验 分为3个目标：首先测试P2 X受体是否是传递味觉信息所必需的。为 在这些研究中，我们将从行为学和电生理学上描述系统的特征，以测试 舌味觉系统的功能。我们还将测试喉部化学感受是否占 这些KO小鼠的剩余行为能力。其次，我们将利用解剖学和生理学 测试敲除小鼠的味蕾在结构和功能方面是否正常的措施。 我们将评估P2 X2/3基因敲除小鼠味蕾的结构和功能，以测试受体细胞是否被激活。 正常的，没有明显的变化，在受体上皮细胞可能是失去味觉功能的基础， P2 X2/3 KO小鼠。在最后的目标中，我们将测试野生型和基因敲除小鼠的味蕾是否会释放 ATP刺激。这些功能性研究将在体外进行，既通过使用β-内酰胺酶， 荧光素酶测定和ATP传感生物探针（所谓的“嗅探细胞”）。此外，我们将利用 奎纳克林负载以评估味觉细胞的囊泡摄取和ATP释放。综合起来， 拟议的研究将测试ATP和亲离子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.