How teeth sense cold temperatures

Cold teeth can be painful, particularly if they’re decayed. In a new paper, published in Science Advances, scientists reveal that they’ve located a protein that lets teeth sense cold temperatures.

The protein, TRPC5, is an ion channel: a molecular tube that can open and shut, letting ions through that trigger electrical impulses. It appears in several parts of the body – in fact, when researchers from the Howard Hughes Medical Institute (HHMI) in the US began to examine it 15 years ago, they looked at its effect in skin.

The researchers were able to show that the protein itself was highly sensitive to cold, but it didn’t seem to trigger any physical responses. In a paper they published in 2011, mice without the protein in their skin weren’t any more sensitive to the cold.

“We hit a dead end,” says team member Katharina Zimmermann, now an electrophysiologist at the Friedrich-Alexander University in Germany. But she continued to mull the problem over with David Clapham, a neurobiologist at HHMI, and their fellow researchers.

A new idea occurred to them while the team was having lunch one day. “David said, ‘Well, what other tissues in the body sense the cold?’,” says Zimmerman. They began to investigate teeth.

This new research shows that TRPC5 is present in teeth, and that it does connect to the nerves. It appears in cells called odontoblasts, which are normally well-protected but can become exposed from tooth decay.

The researchers investigated mice without TRPC5 in their teeth, alongside a control group of mice and teeth that had been treated with a chemical that blocked the protein.

In the control mice, an icy solution touching the teeth prompted a nervous response. Another protein, TRPA1, seemed to have an effect as well. But in the protein-less mice and the treated teeth, there wasn’t any nervous response.

This research also explains why clove oil, which is a centuries-old home remedy for toothache, may alleviate tooth pain. Clove oil contains a chemical that blocks the TRPC5 protein, preventing it from triggering nerves.

The researchers believe this study could contribute to even more effective treatments for tooth pain. “Once you have a molecule to target, there is a possibility of treatment,” says Zimmerman.

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