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Naked mole-rats feel no pain from acid

Naked mole-rats in the Lewin lab.
[Image © Max Delbrück Center for Molecular Medicine]

The African naked mole-rat is, to our eyes, a pretty ugly creature. These small animals have no hair, wrinkly skin, and two long, yellow front teeth. They live in huge colonies inside deep underground tunnels, where there is little fresh air.

Although these animals wouldn't win any beauty prizes, they are special for another reason. Unlike virtually all other mammals, they don't feel pain caused by acid.

If scientists can understand why, it might help them develop pain treatments for humans.

Ewan St. John Smith and colleagues at the Max-Delbrück Center for Molecular Medicine in Berlin-Buch, Germany have now discovered why the mole-rats are insensitive to this kind of pain.

Nerve cells called neurons send and receive signals via proteins called receptors. The scientists have found a genetic difference in a certain piece of the mole-rat's pain receptors. Because of this difference, these neurons don't fire off pain signals in response to acid.

Why would the mole-rat's nervous system have evolved this way? Mole-rats live in an environment with very little oxygen and high levels of carbon dioxide, which makes high levels of acid build up in their tissues. So, this mutation probably helps them survive in this deep underground environment.

This research appears in the 16 December issue of the journal Science.