Chemosensory Function of Ion Channels in Amphibian Skin

与其他脊椎动物不同，两栖动物不喝水。 相反，它们通过皮肤渗透吸收水分，这一过程称为皮肤饮水。 由于经皮肤饮水吸收的水不会进入口腔，因此舌头中的盐味觉受体没有机会评估水的含盐量，但我们实验室先前支持的NSF研究表明，蟾蜍在含有过量盐的水时会避免皮肤饮水行为。 相反，脱水的蟾蜍对少量的盐表现出偏好，这一现象与包括人类在内的哺乳动物对盐的胃口相似，人类可以用舌头品尝盐。该提案支持的研究旨在研究蟾蜍皮肤的感觉功能和细胞机制，使它们能够检测到两栖生活方式所必需的水源中盐的存在。 到目前为止，我们已经发现，通过皮肤感受盐味的细胞机制类似于口服饮料的动物舌头中的味蕾。 下一个支助期的主要目标是：1.识别阳离子（如钠和钾）和阴离子（如氯）穿过皮肤的进入途径，2.识别将感觉信息传递给神经系统的特定受体细胞;以识别将感觉信息从受体细胞传递到神经系统的特定神经细胞。这些研究将使我们能够更好地了解两栖动物和哺乳动物的盐味之间的相似性，以及两栖动物如何应对环境的变化。 两栖动物的数量在全球范围内都在下降，被认为是检测全球环境变化的哨兵物种，但人们对这些动物如何感知环境变化知之甚少。

Unlike other vertebrate animals, amphibians don't drink by mouth. Instead, they absorb water by osmosis across their skin, a process termed cutaneous drinking. Since water absorbed by cutaneous drinking does not enter the mouth, there is no opportunity for salt taste receptors in the tongue to evaluate the salt content of the water, yet previous NSF suported studies in our laboratory have demonstrated that toads will avoid cutaneous drinking behavior when presented water that contains excessive salt. Conversely, dehydrated toads show a preference for a small amount of salt, a phenomenon that is analagous to salt appetite by mammals, including humans, who can taste salt with their tongue.The research supported by this proposal is designed to study the sensory function of toad skin and the cellular mechanisms that allow them to detect the presence of salt in a water sources essential to their amphibious lifestyle. To date we have found that the cellular mechanisms of salt taste by the skin resemble those of taste buds in the tongue of animals that drink orally. The primary goals for the coming period of support are to: 1. identify the route of entry for cations (such as sodium and potassium) and anions (such as chloride) across the skin, 2. to identify specific receptor cells that relay sensory information to the nervous system and 3. to identify specific nerve cells that relay sensory information from the receptor cells to the nervous system. These studies will allow us to better understand the similarities between salt taste in amphibians and mammals and how amphibians respond to changes in their environment. Amphibian populations are known to be declining world wide and are considered sentinel species for the detection of global environmental changes, yet little is known about how these animals actually perceive changes in their environment.