The role of salivary sodium in gustatory responses to salt and water in humans

项目摘要 盐和水的重要营养物质是如何被感知的还不完全清楚。本项目将调查这些 基于初步数据的两个问题表明，唾液中的钠（Na+）是一个重要因素， 对这两种营养物质的感知机制。这种可能性最初是通过一次偶然的发现而被发现的， 在品尝NaCl之前，舌尖接触水会干扰对咸味的感知， NaCl的酸甜副作用。随后的一项实验表明，这些影响可以被抵消， 在水中加入NaCl，浓度与唾液中的Na+相似。这些结果提供了第一个证据， 唾液中的Na+可能对编码人类咸味的质量很重要， 唾液Na+从口腔中的稀释和冲洗用作水的味觉信号。初步的功能磁共振成像 一项研究支持了这一假设，研究表明，增加唾液中NaCl形式的Na+浓度， 显著降低大脑对水的正常反应，特别是味觉皮层。这些数据一起 这表明唾液中Na+提供了一个稳定状态的味觉信号，从该信号中，正偏差是一致的 随着盐的到来，负偏差信号纯水的到来。我们将在初步的 通过3个具体目标测试这一总体假设的数据：目标1将确定唾液Na+是否有助于 通过测量盐的味道质量和强度， 与暴露于含有NaCl的水之后相比，暴露于纯水之后的阈上NaCl，和/或 NaHCO3。还将对KCl和KHCO 3进行检测，以排除渗透压浓度作为一个因素，以及未刺激唾液中的Na+ 将测量（此处和目标2和3），以确定唾液Na+是否有助于个体差异， 感知NaCl副味道。目的2将探讨周边机制和知觉特性 使用乳糖醇阻断甜味受体TAS 1 R2/TAS 1 R3的活性 和阿米洛利阻断钠通道ENaC。最后，Aim 3将使用fMRI来检验假设， 对纯净水的味觉脑反应取决于通过测量 对含有和不含广泛NaCl浓度的水的反应，包括Na+的唾液水平。 KCl将再次进行测试，以排除渗透压作为一个因素，阿米洛利也将用于阻断ENaC， 确定味觉大脑对水的反应是否依赖于通过该通道的Na+信号。

PROJECT SUMMARY How the vital nutrients of salt and water are sensed is not fully understood. This project will investigate these two questions in humans based upon preliminary data that suggest sodium (Na+) in saliva is an important factor in the mechanisms for sensing both nutrients. This possibility first came to light via a chance finding that exposing the tongue tip to water prior to tasting NaCl interfered with perception of saltiness and increased perception of NaCl's sweet and sour side-tastes. A subsequent experiment indicated that these effects could be counteracted by adding NaCl to water in concentrations similar to Na+ in saliva. These results provide the first evidence that salivary Na+ may be important for encoding the quality of salt taste in humans and raises the possibility that rapid dilution and rinsing of salivary Na+ from the mouth serves as a gustatory signal for water. A preliminary fMRI study has supported this hypothesis by showing that adding salivary concentrations of Na+ in the form of NaCl markedly reduces the normal brain response to water, particularly in gustatory cortex. Together these data suggest that Na+ in saliva provides a steady-state gustatory signal from which positive deviations are consistent with the arrival of salt, and negative deviations signal the arrival of pure water. We will build upon the preliminary data to test this overarching hypothesis via 3 specific aims: Aim 1 will determine if salivary Na+ facilitates encoding of NaCl saltiness rather than its side-sides tastes by measuring the taste quality and intensity of suprathreshold NaCl after exposure to pure water compared to after exposure to water containing NaCl and/or NaHCO3. KCl and KHCO3 will also be tested to rule-out osmolarity as a factor, and Na+ in unstimulated saliva will be measured (here and in Aims 2 & 3) to determine if salivary Na+ contributes to individual differences in perception of the NaCl side-tastes. Aim 2 will investigate the peripheral mechanisms and perceptual properties of the sweet and sour side-tastes using lactisole to block activity in the sweet taste receptor TAS1R2/TAS1R3 and amiloride to block the sodium channel ENaC. Finally, Aim 3 will use fMRI to test the hypothesis that the gustatory brain response to pure water depends on rinsing salivary Na+ from the tongue by measuring the response to water with and without a wide range of NaCl concentrations that encompass salivary levels of Na+. KCl will again be tested to rule-out osmolarity as a factor, and amiloride will also be used to block ENaC to determine if the gustatory brain response to water depends upon Na+ signaling via this channel.