St. Louis, June 18, 1998 -- The brain can teach cells in the spinal cord to feel pain, scientists have discovered. Once receptors on these cells are activated, they continue to transmit pain signals even if there is no injury, so blocking them may lead to better treatments for persistent pain.
"Nerve fibers from the brain can help control pain, just like medications," explains Min Zhuo, Ph.D., assistant professor of anesthesiology and neurobiology at Washington University School of Medicine in St. Louis. "Now, we have shown that those fibers also can enhance the transmission between the painful stimulus and the neuron in the spinal cord."
The researchers report their findings in the June 18 issue of the journal Nature. The study was funded, in part, by a grant from the National Institute on Drug Abuse.
When we encounter a painful event, receptors on the skin, muscle or internal organs trigger an electrical impulse that travels along a nerve fiber to the dorsal horn of the spinal cord. That fiber connects with a nerve cell, which passes the pain signal up the spinal cord to the brain. Because the signals cross junctions -- synapses -- on their way to the brain, they can be modified en route. For example, opioids prevent signals from getting across synapses, thus preventing patients from feeling pain.
The brain also can block pain by preventing signals from crossing synapses. That may be why some soldiers can continue to fight even though they are gravely wounded. The investigators found that the brain also can enhance pain by activating silent synapses, however. A brain region called the rostroventral medulla (RVM) sends a chemical signal to cells in the dorsal horn of the spinal cord, they discovered. The neurotransmitter serotonin activates silent synapses in dorsal horn neurons.
Inefficient, or silent synapses were proposed more than 20 years ago,
but technical limitations prevented detailed studi
Contact: Jim Dryden
Washington University School of Medicine