Emerging Science Note/Stress and Chemicals
Living on Earth’s Cynthia Graber reports that stress may intensify the effects of chemicals on the brain.
CURWOOD: Just ahead: 800,000 dollar veterinarian bills and the people who pay them. First, this note on emerging science from Cynthia Graber.
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GRABER: Pharmacologist Mohamed Abou Donia at Duke University has spent more than ten years trying to figure out why soldiers from the first Gulf War suffer from what’s called Gulf War syndrome. They complain of aches and pains, fatigue, loss of memory, and of difficulties concentrating and learning. Doctors have been unable to discover the cause of the soldiers’ complaints. Now, Abou Donia believes he may have found one possible explanation of why the soldiers continue to suffer.
Soldiers during the war were exposed to an anti-nerve gas agent, the skin-applied insecticide Deet, and a clothing insecticide called permethrin. The levels of these chemicals had been tested and were considered safe. The soldiers also experienced a great deal of stress during the war. In previous experiments, Abou Donia demonstrated that exposure to a mixture of these chemicals can have more of an effect than individual chemical exposure. He also knew that stress has been shown to cause neurological damage. So he set out to test whether stress can intensify the effects of chemicals.
Abou Donia took four groups of ten rats. One group was exposed to the chemicals, in doses that were analogous to those the soldiers received. A second group of rats received what’s known as psychological stress for animals – they had their movement restricted for just five minutes a day. The third group received the chemicals and the stress. And the fourth group received nothing. After 28 days, all the rats looked and behaved normally. So the group of scientists killed the rats and examined their brains. The rats that were exposed to chemicals showed little brain damage. Those subjected to stress also had healthy brains. But the mix of chemicals and stress produced surprising results.
In those rats’ brains, cells died in significant numbers in the cerebral cortex, the hippocampus, and the cerebellum. These are areas that control functions such as learning and memory, motor function, and muscle coordination. There was also a change in brain chemicals necessary for learning, memory, and for muscle strength and movement. Finally, this stress plus chemical combination also increased destructive molecules in the rats’ brains called reactive oxygen species, or oxygen free radicals. These attack and damage different parts of cells.
Abou Donia believes it’s this increase in free radicals that caused the brain damage. Current MRIs are not sensitive enough to measure changes in human brains on the scale of what Abou Donia has seen in the rats. So even if Gulf War veterans had similar damage, it would be extremely difficult to detect. But Abou Donia hopes in the future this research can lead to methods for preventing symptoms such as those suffered by the veterans. That’s this week’s note on emerging science, I’m Cynthia Graber..
CURWOOD: And you’re listening to Living on Earth.
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