Viewed under a microscope, your tongue is an alien landscape, studded by fringed and bumpy buds that sense five basic tastes: salty, sour, sweet, bitter, and umami. But mammalian taste buds may have an additional sixth sense—for water, a new study suggests.
Ever since antiquity, philosophers have claimed that water has no flavor…But insects and amphibians have water-sensing nerve cells, and there is growing evidence of similar cells in mammals, says Patricia Di Lorenzo, a behavioral neuroscientist at the State University of New York in Binghamton.
In an attempt to settle the debate, Yuki Oka, a neuroscientist at the California Institute of Technology in Pasadena, and colleagues searched for water-sensing taste receptor cells (TRCs) in the mouse tongue. They used genetic knockout mice to look for the cells, silencing different types of TRCs, then flushing the rodents’ mouths with water to see which cells responded.
When given the option of drinking either water or a clear, tasteless, synthetic silicone oil, rodents lacking sour TRCs took longer to choose water, suggesting the cells help to distinguish water from other fluids.
[Read the full study here (behind paywall)]
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