Naked Mole Rats May Hold Clues to Surviving Stroke
[Writer] This is research news from U-I-C – the University of Illinois at Chicago. Today John Larson, associate professor of psychiatry, talks about studies that he and biology professor Thomas Park performed using naked mole rats. The research revealed the rodent can withstand up to a half hour of hypoxia – or oxygen deprivation – which may provide clues useful in developing new treatments for stroke.
Here’s Professor Larson:
[Larson] We’ve been studying the physiology of the brains of naked mole-rats. These naked mole- rats are very unusual for a number of reasons. First of all, their lifestyle is rather strange to us. They live under ground almost all of the time. They hardly ever come out of their burrows. They have large numbers of animals living together in a single burrow system. They have an unusual social structure in that there’s only one breeding female per colony – a queen, if you will. And there’s a very strict division of labor amongst the other animals in colony – there are some that will work for defense, some that work for gathering food, and so forth.
They also have a number of interesting physiological adaptations to this environment, and there are some peculiarities of these animals that we don’t understand, quite frankly. One of the most interesting is that they’re very long-lived animals. They’re about the same size as a mouse. Ordinarily, as a rule, bigger animals live longer than smaller animals, but here we have two species that are about comparable in body size, but one lives about 10 times longer than the other.
They don’t seem to get cancer. They don’t regulate their body temperature physiologically. And they live in an environment that is very low in oxygen, so they seem to be very hypoxia-tolerant – that is, able to withstand chronic atmospheres that are low in oxygen.
I’m a neurophysiologist, and what we study in my lab is brain functions – particularly how brain cells communicate with each other in a process called synaptic transmission. The brain is the organ in the body that consumes most of the energy that’s produced in the body. So we look at oxygen consumption, for example. The human brain consumes about 20 % of the oxygen that’s taken in by the body. So what goes on in the brain is very metabolic-dependent, and it’s very crucial that there’s a constant supply of oxygen to the brain at all times. Even very brief periods of oxygen depravation, or what’s called ischemia – when there’s a loss of blood flow to the brain – can very quickly cause cell death. And if widespread throughout the brain and prolonged enough in time, will cause death. This is what can happen during strokes, heart attacks and so forth.
So, we were interested in seeing if the naked mole-rat brain tissue has adaptations that allow it to maintain its function in a low-oxygen environment. So we tested this in a couple of different ways. We measured the process of synaptic transmission in response to reduced levels of oxygen that we could supply experimentally. We found that compared to typical rodents, like mice, the naked mole-rat brain can maintain its function at levels of oxygen one-third to one-half as high as were required for an animal like a mouse. A second type of experiment we did was to actually cut off the oxygen supply to the brain tissue completely and measure how long it takes until it fails in its electrical and chemical activity. We found that this took three to four times longer in the naked mole- rat brain than in the mouse brain.
Now we know that in mammals, in general, animals that are very young – in the post- natal period – are hypoxia resistant. Our working hypothesis is that the naked mole-rat brain, even at adulthood, fails to develop in the same way that normal mammal brains do, and that it retains some of this resistance to hypoxia that is seen in neo-natal mammals in general, even in the adult naked mole-rat. So we’d like to understand the mechanisms that are responsible for this, because that may lead to treatments that could be used un conditions that happen to people when the supply of blood to the brain is cut off for periods of time that can happen with drowning, or strokes, or with heart failure.
[Writer] John Larson is associate professor of psychiatry.
For more information about this research, go to www.today.uic.edu … click on “news releases.” … and look for the release dated November 30, 2009.
This has been research news from U-I-C – the University of Illinois at Chicago.
