A study conducted by researchers from Duke University in Durham, North Carolina, have found that the amygdala in mice's brain can significantly control their sense of pain.
According to Fan Wang, the lead author of the study and the Morris N. Broad Distinguished Professor of neurobiology in the School of Medicine, recent studies have determined parts of the brain that could 'turn on' pain signals, but this was the first time they were able to pinpoint where pain could be 'turned off.'
The researchers also discovered that general anesthesia also stimulates a specific subgroup of inhibitory neurons in the central amygdala called the CeAga neurons. Although mice have a comparably bigger central amygdala than humans, Wang says she doesn't think there would be any difference in the two brain systems from controlling pain.
The mice were initially given a pain stimulus, and the researchers mapped out the brain's pain-activated regions. They then uncovered that about 16 brain centers that could process the sensory or emotional aspects of pain were receiving inhibitory pain input from the CeAga.
When the scientists diminished the activity of these CeAga neurons, the mice responded and displayed behavior indicating intense pain. They also determined that low-dose ketamine activated the CeAga center and wouldn't function without it.
The team's next step is to search for drugs that can activate only these specific cells to suppress pain. According to Wang, they could potentially develop pain killers in the future using their discoveries from the study.
The team's research 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.
The findings of their study were published in the journal Nature Neuroscience on May 18.
Fight of Flight Center Now Also an Off Switch for Pain
The amygdala is an almond-shaped collection of nuclei found deep in the temporal lobe of the brain. It is a part of the limbic system and is believed to be heavily involved with behavior and emotion.
When we experience situations that can bring about fear, information about that stimulus is sent to the amygdala, which then sends signals to other parts of the brain like the hypothalamus to trigger a "fight-or-flight" response.
The amygdala is also thought to be involved in the fortification of memories with strong emotional components. These memories are kept regardless of whether they are associated with positive or negative emotions. Experts believe that our knowledge of the function of the amygdala is still evolving and that future studies will uncover more things.
A Painful Problem
Wang says that pain is a complicated brain response that deals with emotion, sensory discrimination, and autonomic responses.
The Center for Disease Prevention and Control estimated that one in five American adults had chronic pain in 2016. Furthermore, about eight percent of adults in the US had chronic pain that limited their life and work activities on most days or every day during the past six months.
Additionally, the Institute of Medicine reports that chronic pain is a growing public health concern in the United States. Costs regarding pain were recorded at an estimated $560 billion each year for medical care, disability services, or lost productivity.
Many researchers like Wang are working to find advancements to solve this rising universal problem affecting millions of people worldwide.
