Can a Bitter Taste be Detected Outside the Tongue?

Bitter, sweet, sour, salty, and savory tastes can be sensed by the tongue through their related taste receptors. The taste of bitter is very important in nature. It protects us from eating harmful things, which usually taste bitter. In this research, we looked for cells that have bitter taste receptors. To make them visible, we labeled them with a green fluorescent protein. These green cells were found on the tongue, as expected, but they were also found in other places that are easily exposed to harmful things, such as the airway, the gut, and the urethra. Our work also showed that the cells expressing bitter receptors could have the ability to activate the immune system. We cannot actually taste bitter anywhere apart from the tongue, but bitter taste receptors in other parts of the body may function in a different way.