We don’t think about the taste of water very much, despite the fact that we’d have been dead long ago without a way to sense the substance that makes up 50 to 60 percent of our bodies. There is something, somewhere, in the mouth that tells us we are drinking it. Mouse research has previously indicated that drinking water triggers the firing of nerves that ferry taste information from the mouth to the brain. And now, scientists publishing in Nature Neuroscience have pinpointed a specific set of taste cells in mice that cause these nerves to fire. Surprisingly, they are cells we are already quite familiar with.
The researchers began by testing mice that each lacked the ability to sense one of the five basic tastes: sweet, bitter, umami, salty, and sour. Some mice had been genetically engineered to lack a protein important to their missing taste; others were normal but had been treated with a drug that kept certain taste cells from functioning, or exposed to a toxin that destroyed their function. The idea, says Yuki Oka, a professor at the California Institute of Technology who led the study, was that if any of the hampered taste cells were responsible for sensing water, the taste nerves would no longer fire when researchers gave the mice a drink. But they didn’t actually expect that to happen: They had hypothesized that there would turn out to be another, as-yet undiscovered group of cells doing the job.