October 27, 2016

PAIN-FREE STUDY

Naked mole-rats are strange animals. Researchers are interested in them for several reasons. They live for over 30 years. This is far longer than other animals of a similar size. Na-ked mole-rats almost never get can-cer. Also, they don’t feel some types of pain. Oddly, the creatures run as fast backwards as they do forwards.

Scientists working in Germany have been studying naked mole-rats. They want to better understand why the animals are not affected by pain. The scientists have been mon-itoring 120 naked mole-rats. All are living in the scientists’ laboratory in Berlin, Germany’s capital city. The animals live in groups known as colonies. The laboratory mole-rats are divided into six colonies. In the wild, 300 naked mole-rats might live in one colony.

Naked mole-rats are not moles or rats. One of their closest relatives is the guinea pig. As its name suggests, the naked mole-rat is hairless. It has no fur. The animals are found only in the East African countries of So-malia, Ethiopia and Kenya. There, they are also called the sand puppy or desert mole-rat. The animals live under ground in hot dry, or desert, areas. They spend most of their lives in darkness.

Fully-grown naked mole-rats are about four inches (ten centimeters) long. Nearly all mammals control their internal body temperature. This stays the same whether the weather is hot or cold. Naked mole-rats are different. Their body temperature matches the surrounding temperature. If it is hot, the mole-rats are hot. If it is colder, their internal temperature

goes down. Naked mole-rats feed on root tubers. These are the large parts of some plants that grow under the ground. Carrots are root tubers.

Naked mole-rats have two long lower teeth, or incisors. These do not fit inside their mouths. The animals use the teeth to dig their underground tunnels. Unusually for mammals, naked mole-rats are what’s known as eusocial. Ants and termites are eusocial. Like ants and termites, a naked mole-rat colony has a queen, soldiers and workers. The queen will mate with one, two or three males. Workers dig tunnels and look after the young. Soldier mole-rats defend the colony from snakes and other mole-rats.

In humans, one type of pain is caused when heat is applied to an inflamed area of skin. For instance, a warm bath will make sunburned skin even more painful. Inside the body, two things joining, or binding, together, cause this pain. These are molecules called nerve growth fac-tor (NGF) and a pain receptor. Most mammals feel this type of pain. Naked molerats don’t.

In a naked mole-rat, the NGF joins with the pain receptor. Yet it is a very weak link. The scientists discovered that if the NGF were increased by a factor of ten, the mole-rat would feel it. The scientists took pain receptors from a mole-rat and put them inside cells from a rat. Then, the rat cells did not notice the pain. The mole-rat’s pain receptors seem to be “switched off”, or “turned down”.

The scientists suspect that the naked mole-rats have switched off pain receptors for a reason. Pain acts as a warning system for most animals. It tells them to stop what is happening, or what they are doing. If they don’t, their injury will get worse. In mole-rat colonies it can be very crowded and hot. There is not much oxygen in their tunnels. If a person were in these conditions, it would be difficult to breathe. Their pain receptors would be “always on”. This is how naked mole-rats live. Therefore they have evolved in a way that means their pain recep-tors are “always off”.

The scientists plan to continue their studies. Eventually, they hope to use naked mole-rats to create pain-relief treatments for humans.