A small area of the brain can control one's sense of pain, a new study from Duke University suggests. Sixteen brain centers receive inhibitory input from the CeAga.
The researchers detected a small area of the brain in mice that can deeply control the sense of pain in the animals.
This part of the brain is found in the amygdala, which is considered the source of negative emotions and responses.
"People do believe there is a central place to relieve pain, that's why placebos work," said senior author Fan Wang, the Morris N. Broad Distinguished Professor of neurobiology in the School of Medicine. "The question is where in the brain is the center that can turn off pain."
"Most of the previous studies have focused on which regions are turned ON by pain," Wang said. "But there are so many regions processing pain, you'd have to turn them all off to stop pain. Whereas this one center can turn off the pain by itself."
General anesthetics
The current study is based on an earlier research in Wang's laboratory that investigates activated neurons, instead of those that are suppressed, through general anesthetics.
A 2019 study revealed that general anesthesia sparks slow-wave sleep through the activation of the supraoptic nucleus of the brain. However, sleep and pain are separate, an important clue that led to the new finding, which appears online May 18 in
Published in Nature Neuroscience, the study "General anesthetics activate a potent central pain-suppression circuit in the amygdala" highlighted the role of general anesthesia in activating a specific subset of inhibitory neurons in the central amygdala, which were labeled as the CeAga neurons. CeA refers to central amygdala; ga hints activation by general anesthesia.
Meanwhile, mice possess a larger central amygdala than humans. Wang noted she had no reason to believe it is different from human's system of controlling pain.
The researchers discovered the link of CeAga to many different areas of the brain, "which was a surprise," Wang admitted.
With the mild pain stimulus given to the mice, the pain-activated brain regions were easily identified. Findings showed that at least 16 brain centers that are involved in the sensory or emotional aspects of pain were getting inhibitory input from the CeAga.
"Pain is a complicated brain response," Wang said. "It involves sensory discrimination, emotion, and autonomic (involuntary nervous system) responses. Treating pain by dampening all of these brain processes in many areas is very difficult to achieve. But activating a key node that naturally sends inhibitory signals to these pain-processing regions would be more robust."
Pain killers
Meanwhile, the researchers aim to seek drugs that can activate only these cells to control pain as potential future pain killers, Wang said.
"The other thing we're trying to do is to (transcriptome) sequence the hell out of these cells," she said.
Her team wants to detect the gene for a rare or unique cell surface receptor among these specialized cells. These would allow a specific drug to keep the neurons activated and ease pain.
The study was supported by the National Institutes of Health, the W.M. Keck Foundation, the Holland-Trice Scholar Award, and a predoctoral fellowship from the National Science Foundation.
