Naked Mole-Rats Bear Chili Pepper Heat
[Writer] This is Research News from U-I-C, the University of Illinois at Chicago.
Today, Thomas Park, associate professor of Biological Sciences, talks about research using gene therapy to restore sensation in naked mole rats, rodents that lack a neurotransmitter that causes prolonged pain in other mammals.
Here’s Professor Park:
[Park] The research I do involves a very strange animal, the African naked mole rat, which looks very much like an undercooked sausage with buck teeth. And what we’ve been doing with naked mole rats is measuring some of the unusual responses they have to stimulation with different types of touch. For instance, if we touch a naked mole rat with something sharp, it pulls its foot away. But if we touch it with something like capsaicin, the spicy ingredient in chili peppers, it doesn’t seem to find that as a problem at all. And that is very different than other mammals. Now what we’ve done is, we have found that naked mole rats are missing a very basic neurochemical from the nerve fibers that normally respond to painful chemicals like capsaicin and acids like lemon juice. So, we went on to test those types of stimuli and found that these animals are absolutely insensitive to those types of stimulation. What we did then was to say, “Well if they’re missing this basic neurochemical, which is called Substance P, if we put that back into the nerve fibers, would they then be able to feel pain?” And what we’ve found is both yes and no. If we put Substance P back into the system using a retrovirus and gene therapy techniques, what we find is that they become very sensitive to capsaicin, the chili pepper ingredient, but they’re still insensitive to acid. And I want to say that naked mole rats are the only animal ever tested that is insensitive to acid stimuli. And that includes fish, frogs, birds and mammals.
Ok so what we think is the reason behind their insensitivity to these different stimuli is the way that they have evolved in nature. So naked mole rats are unusual in a number of ways. They live in very large social colonies of hundreds of animals and they live underground where the air becomes very foul, low oxygen, high carbon dioxide. And what happens in a high carbon dioxide atmosphere is that the CO2, the carbon dioxide, as they breathe out, becomes an acidic chemical when it touches their skin, eyes, nose and mouth. And what we believe is that they have evolved such that acid stimulus is no longer painful for them as it is to everybody else.
So, what can we learn from studying an animal that has a bizarre adaptation like this? Well, one thing we can learn is which type of nerve fibers are involved in coding which kinds of pain. Now the naked mole rats are completely insensitive to the long-lasting types of pain that we think of coming from joint injuries, pulled muscles or post-surgical recovery, and that’s the kind of pain that many times we think of as bad pain. We’d love to go and have our appendix out but not have to be on our back for two days waiting for that long-lasting, post-operative pain to go away. And this is the type of pain that naked mole rats appear to be completely insensitive to. So if we can learn how they’ve done it, then we can apply what we learn to people that are having problems with long-lasting pain, including chronic pain disorders.
[Writer] Thomas Park is an associate professor in Biological Sciences.
For more information about this research, go to www-dot-news-dot- uic-dot-edu … click on “news releases” … and look for the release dated January 29, 2008.
This has been research news from U-I-C – the University of Illinois at Chicago.