When you sprain your ankle, it swells up, turns red, and hurts when you touch it. After a sunburn, a similar thing occurs with redness and your skin is sensitive to heat and touch. And the same thing happens in an infection — have you ever noticed after a sore throat, your throat swells up, and swallowing hurts?

Did You Know?
The body responds to injury or infection by activating the immune system to cause redness, warmth, swelling and pain. This response is called inflammation, and is part of the body's normal healing process. Why does inflammation hurt? There are a few reasons:

A) To notify you that there is something wrong

B) To prevent further damage by limiting movement and function

C) To allow the body to repair the damaged tissue.

Most of the time this response is able to fix whatever went wrong and the body can return to normal. But there are a few cases when the body cannot repair itself, and the inflammation persists resulting in disease. An example of this would be the painful condition arthritis.

Wouldn't it be awesome if there was a way to make it so that we no longer felt pain after we got an injury or infection?

Interestingly enough, this goal might just be realized by studying one of the strangest creatures on this planet. Scientists have just discovered that inflammation causes very little pain in animals called naked mole rats. This is important because studying these animals may lead to new treatments (painkillers!) for inflammatory pain conditions like arthritis.

If there was a single word to describe naked mole rats, ugly might be it — they have wrinkly skin, almost no hair, and giant teeth. (But then again, if I was near blind and lived underground in the dark my entire life I wouldn't really put looking good at my top priority either.) Nevertheless, these animals are truly fascinating, and scientists have much to learn about them. For instance, naked mole rats live extraordinarily long lives for rodents. They have been observed to live up to 28 years of age, whereas mice, which are similar in size to naked mole rats, live typically only 2.5 years. Naked mole rats are also the only cold-blooded mammals known on this planet. Furthermore they have a very complex social system similar to that of ants and bees which is again incredibly rare in mammals.

Why do these creatures experience reduced inflammatory pain anyway? The answer is that these animals lack a neurotransmitter called Substance P in the skin. When this missing neurotransmitter is reintroduced, interestingly the naked mole rats revert to the same pain signalling as in other mammals.

Did You Know?
Substance P is a neurotransmitter which transmits painful information to the brain.

The observation that substance P is required for pain helps to explain how some drugs work. For example, capsaicin (the spicy component of chilli peppers), is used in humans as a drug to alleviate pain. Capsaicin depletes substance P from nerve terminals over the long-term, and this reduces the amount of substance P available to transmit painful information to the brain.

And why did naked mole rats lose this pain neurotransmitter? Scientists hypothesize that it has to do with their living conditions. In the underground burrows of the naked mole rats, CO2 can build up to high levels. High levels of CO2 can build up in tissue as an acid, which, at least in you and me, results in a burning pain. For example, this is why muscles ache after an intense workout. As lactic acid and CO2 builds up, this results in pain. Fortunately for the naked mole rat, they evolved so that they cannot feel acid pain, and the lack of inflammatory pain is perhaps a by-product of this evolutionary adaptation.

Learn more!

The naked truth about mole-rats

Naked mole-rats may resemble hot dogs with teeth, but pain researchers still find them attractive

Selective inflammatory pain insensitivity in the African Naked Mole-Rat

Tony Lim received his BSc in Pharmacology from the University of British Columbia (Vancouver, BC) and is now pursuing an MSc at McGill University (Montreal, QC), also in the field of Pharmacology. He loves science and is very passionate about it – he chose to study pharmacology because he hopes that one day he can create drugs that improve the lives of the ill and save lives. When he’s not busy at research, he’s often found playing badminton, volleyball or reading manga.

Tony Lim

I am a graduate student pursuing a PhD in the neuroscience program at McGill University. In addition to neuroscience, my scientific interest and background lies in the field of pharmacology. When not at the lab, I enjoy playing volleyball, badminton, snowboarding and playing electric guitar with the band in my spare time.


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