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A team of scientists from Stanford University identified a brain cell cluster in the mouse responsible for the latter, that is, the negative emotions of pain.
Backed by animal brain imaging and molecular testing, badysts have discovered a set of cells in the amygdala, a region of the brain traditionally connected to feeling and fear, that seems to work explicitly as a walk-through switch. stop painful aversion.
Moreover, despite the fact that the discovery was made in the mouse, there is a motivation to think that it could be replaced today as a way to remedy human pain, since the mouse and amygdala human beings have the same function.
According to scientists, studying this group of cells could reveal a potential treatment for chronic pain.
Irene Tracey, a pain neuroscientist at Oxford University who did not participate in the study, said, "This study is a breakthrough. It was a tour de force and a welcome addition to understand this complex and major problem. "
For this study, scientists used a miniature microscope, or miniscope, to sift through the entanglement of neurons and identify those badociated with pain.
Mark Schnitzer, neuroscientist at Stanford, said, "The miniscope allows you to track neurons over time, while the mouse behaves normally."
Scientists began by introducing a fluorescent protein into the amygdala that releases a tiny discharge of light when the neurons are triggered. Then the team guides this thin, deep object into the brain to see what neurons are flashing when the mouse reacts to painful stimuli, such as needle sticks.
At the point where a mouse is in pain, it retires reflexively, as our hand does when we contact a hot stove. Scherrer says that these reflexive behaviors show the sensation of pain, but are not undesirable. Different behaviors, such as avoiding the painful stimulus or licking the paw that touched it, show that the pain is unpleasant.
The scientists exposed the mice to various benign and painful stimuli and identified a constellation of about 150 neurons in a region called the basolateral tonsil that was active only when the mice appeared to be suffering. In addition, it seemed that the more the mouse felt pain, the more this BLA constellation was glowing.
Grégory Scherrer, who co-directed the study, said, "At this point, we could only see that these BLA neurons correlated with pain, but not if they coded the pain inconvenience. "
"To answer the question, we then turned to the creation of chemical switches to control painful neurons. They could then turn off those painful neurons and see if a mouse was behaving differently when it was pricking itself.
Jordan McCall, neuroscientist at Washington University in St. Louis, said, "Getting these switches on the neurons of pain, and only the neurons of pain, required genetic manipulations. This article really combines the most advanced techniques in neuroscience. "
"With the switches in place, we disabled the BLA pain neurons and found that the mice still felt the pain, but they did not behave as if they were uncomfortable."
Scherrer said, "They did not care about pain anymore."
The results resisted when the researchers examined mice that developed chronic pain. The neurons of their BLA torment were found to be sensitive to the point where they let themselves go at the slightest touch. By the time Scherrer killed their BLA pain neurons, the mice still encountered light touch, but did not seem to encounter it as undesirable.
The results suggest that the discomfort of acute and chronic pain comes from these BLA pain neurons, making it a target for the treatment of pain.
Scherrer said, "Opioids can be effective in relieving pain, but they are a blunt tool and affect areas of the brain badociated with behaviors as diverse as addiction and breathing, for example. Now that we know that neurons give pain its annoyance, we can look for receptors found only in these neurons and not in other areas of the brain. "
Schnitzer said: "If there are unique receptors for these neurons, researchers could try to design drugs that reduce their activity. If the approach works, it can lead to a drug that makes the pain more bearable, but does not cause a dull feeling. "
The study is published in the journal Science.
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