Painkillers without side effects
Scientists may have found a substance that blocks chronic pain but doesn't appear to cause the unwanted side effects of other painkillers.
Researchers led by Hanns Zeilhofer at the University of Zurich in Switzerland found the compound after exploring the way pain signals travel up to the brain via the spinal cord.
"Normally the spinal cord acts as a kind of filter, ensuring that not all painful signals coming from the periphery of the body reach the brain," said Zeilhofer.
If these neurological gatekeepers were totally absent, even the lightest touch on the skin would make us wince with discomfort, he explained. "We would be in constant pain without them."
But in patients with chronic pain, this filter function is impaired, meaning that the spinal cord is like an open channel for pain signals, he said.
A key role in the inhibition process is played by two nervous-system chemicals, called neurotransmitters. One is gamma-aminobutyric acid, also known as GABA, and the other is glycin.
"We thought we could restore the filter function if we pharmacologically enhance the action of GABA or glycin in the spinal cord," said Zeilhofer. But as no compounds had been developed that target glycin, they focused instead on GABA.
In experiments reported in the British journal Nature, the researchers induced inflammation in the paws of mice and rats, and then gauged the force needed to make the animal withdraw its leg, creating a rough measure of pain.
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