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THURSDAY, June 26, 2003 (HealthDayNews) -- Scientists have long been interested in a substance called nocistatin, a brain peptide that could play a role in stopping the chronic pain that plagues about 86 million Americans.
German researchers have discovered more clues about how nocistatin might stop the pain process, and how it might act as a kind of natural analgesic by inhibiting the release of a neurotransmitter that's crucial for the pain process to kick in.
"Our main finding is very much related to basic research and questions of communication between nerve cells," says Dr. Hanns Ulrich Zeilhofer, a professor of molecular neuropharmacology at Erlangen-Nurnberg University. He and his colleagues report their findings in the June 27 issue of Science.
The team focused on receptors in the spinal cord called NMDA (N-methyl-D-aspartate), which play a key role in the processing of pain. The receptors require two neurotransmitters, glutamine and glycine, to be fully activated. It is thought that special "transporters" sweep up most of the glycine before it reaches the receptors, so the receptors remain subdued and pain does not become chronic.
But when Zeilhofer's team induced acute pain in laboratory rats, the rats' neurons released enough glycine to overwhelm these transporters. Then the glycine spilled over to the receptors, setting into motion the neurological "cascade" that leads to chronic pain."This process is called spillover," says Zeilhofer. "It has long been thought that synaptically released glycine [released from the synapses, or junctions between cells] only acts on inhibitory glycine receptors located directly in the glycinergic synapses. We have shown, under certain conditions, synaptically released glycine can escape these synapses to act on neighboring excitatory NMDA receptors."
Then came the finding that nocistatin can act as an analgesic by inhibiting this spillover release of glycine.
"We do not know yet whether it really can prevent chronic pain, but it reduces NMDA receptor activation and NMDA receptors are believed to be important for the induction of chronic pain," Zeilhofer says.
"We have previously shown that nocistatin inhibits glycine release," he says. "Others have already shown that nocistatin can be analgesic," he says.
"We are the first to provide a cellular and molecular mechanism for the analgesic action of nocistatin," he adds.
"It's an interesting mechanism to help understand how chronic pain can be perpetuated and amplified," says Dr. Daniel B. Carr, a pain expert at Tufts-New England Medical Center in Boston. "It adds to existing knowledge," he adds, noting that the progression of pain from acute -- considered normal, as when the body warns of danger -- to chronic is complicated.
Acute pain is considered a normal sensation, triggering the nervous system to alert you to potential injury and the need to take action (such as removing your hand from a hot stove). But chronic pain can persist for weeks, months or years. It can involve headache, backache, arthritis pain, and other ailments.
The chronic pain that plagues about 86 million Americans leads to losses of about $90 billion a year, the American Chronic Pain Association estimates. Treatments currently include medication, electrical stimulation, surgery, acupuncture and a variety of other methods.
More information
For more information on chronic pain, try the National Institute of Neurological Disorders and Stroke or the American Chronic Pain Association.
