JUN 04, 2017 9:53 AM PDT

Sour Taste Cells Also Sense Water

WRITTEN BY: Carmen Leitch

Research using optogenetics, which utilizes light to manipulate gene expression, has found that taste cells that sense sour also function in the detection of water on the tongues of mice. After simulating the taste receptors, in response to stimulants of flavor as well as water, the Caltech researchers were surprised to find water was also eliciting a response. Their findings have been reported in Nature Neuroscience

"The tongue can detect various key nutrient factors, called tastants— such as sodium, sugar, and amino acids—through taste," said Yuki Oka, an Assistant Professor of Biology. "However, how we sense water in the mouth was unknown. Many insect species are known to 'taste' water, so we imagined that mammals also might have a machinery in the taste system for water detection.”

The brain receives information about taste from taste nerves, which transmit the stimuli received by taste cells. First author Dhruv Zocchi, a graduate student in Oka’s lab took measurements of how taste nerves responded to various tastes in mice. While the expected results were seen, and the nerves responded as expected to various flavors, there were also responses to water. "This was exciting because it implied that some taste cells are capable of detecting water," Zocchi said.

To zero in on which population of taste cells were detecting the water, the researchers stopped the function of specific taste cells with genetic and pharmacological tools. As such, the investigators could stop the response to salt stimuli for example, while the other taste receptors remained unaffected.

"To our surprise, when we silenced sour taste cells, water responses were also completely blocked," Oka said. "The results suggested that water is sensed through sour taste cells.”

The team wanted to confirm their findings with optogenetics; sour taste cells in genetically engineered mice could then be stimulated with light, instead of water (shown in the video, from the Oka lab). The water spout used by the mice was then replaced with a spout that emitted blue light when touched. Thirsty mice would go to the spout and since they received a stimulus that made them sense water, they continued to lick the spout even though it did not actually dispense water.

Sour flavors are typically associated with unpleasant tastes that will reduce an animal’s inclination to liquid, such as lemon juice, a drink avoided by mice. In the optogenetically engineered mice however, stimulating the sour cells with light did not create an aversion.

"These results raise the question: What information about taste are sour cells really relaying to the brain?" Zocchi explained. "Maybe sour cells are not directly linked to the unpleasant sourness that we perceive, but instead they may induce a different type of taste, like water, when stimulated.”

"It's important to note that stimulation of these cells does not alleviate thirst," continued Oka. "But this finding helps us understand how the brain interprets water signals under normal and thirsty states. Next, we would like to tackle the mechanisms by which the hedonic value or 'pleasantness' of sensory inputs are regulated by brain activity.”

 

Learn more about the senses of taste and smell from the video.

 

Sources: AAAS/Eurekalert! via Caltech, Nature Neuroscience

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
DEC 20, 2019
Genetics & Genomics
DEC 20, 2019
Can We Cure Down's Syndrome with Gene Therapy?
Down’s Syndrome (DS) is a genetic disorder brought on by the presence of all of part of a third copy of chromosome 21. Linked to delays in physical g...
DEC 22, 2019
Microbiology
DEC 22, 2019
Viruses Can Escape the Effects of CRISPR by Shielding Their Genomes
Our world is filled with microbes, and in every kind of environment, they compete for supremacy, a competition that dates back to the origins of life....
FEB 03, 2020
Cell & Molecular Biology
FEB 03, 2020
Brain Organoids May Not be Living Up to the Hype
Cells can be grown in special ways to create three-dimensional, miniature models of organs. But how good are they?...
FEB 04, 2020
Immunology
FEB 04, 2020
The Gut Deploys Protective Mechanisms in Coordination with Your Mealtime Habits
At mealtime, every mouthful of food contains a possible risk of incoming pathogens to the digestive system. The gut takes protective measures to account fo...
FEB 06, 2020
Cell & Molecular Biology
FEB 06, 2020
Taking a Closer Look at a Disease-Linked Protein
Misfolded proteins are closely linked to many neurodegenerative disorders. Researchers have learned more about one of those pathogenic proteins....
FEB 16, 2020
Cell & Molecular Biology
FEB 16, 2020
Growing Cells on Scaffolding as an Alternative to Animal Models
Researchers may have just made it easier for investigators to switch to an engineered model and replace their animal colonies with electrospun synthetics....
Loading Comments...