Stanford Researchers Find the Brain Cells That Make Pain Painful

By HANAE ARMITAGE

STANFORD UNIVERSITY, CA -- If you step on a tack, neurons in your brain will register two things: that there’s a piercing physical sensation in your foot, and that it’s not pleasant. Now, a team of scientists at Stanford University has identified a bundle of brain cells in mice responsible for the latter — that is, the negative emotions of pain.

Pain research has traditionally focused on the neurons and molecules at the frontline of pain perception — the cells in nerves that process stings, cuts, burns and the like — and ultimately convey a physical threat message. What Grégory Scherrer, PhD, assistant professor of anesthesiology and of neurosurgery, and Mark Schnitzer, PhD, associate professor of biology and of applied physics, are studying goes one step further.

“We’re looking at what the brain makes of that information,” Scherrer said. “While painful stimuli are detected by nerves, this information doesn't mean anything emotionally until it reaches the brain, so we set out to find the cells in the brain that are behind the unpleasantness of pain.”

Backed by animal-brain imaging and molecular testing, the researchers have found an ensemble of cells in the amygdala, a region of the brain classically associated with emotion and fear, that seems to specifically function as an on-off switch for pain aversion. And although the finding was made in mice, there’s reason to think it could one day serve as a therapeutic target for human pain, since the mouse and human amygdala aren’t so different in function. Researching this group of cells could reveal a potential treatment for chronic pain, the scientists hope.

The idea is that patients suffer from the emotional unpleasantness of pain, rather than pain sensation itself. If there’s a way to dull the emotional hurt, rather than the physical sensation of pain, that could be big for chronic pain patients.

A paper describing the results of the study were published Jan. 18 in Science. Scherrer and Mark Schnitzer, PhD, who is also a Howard Hughes Medical Institute investigator, share senior authorship. Postdoctoral scholar Gregory Corder, PhD and former graduate student Biafra Ahanonu, PhD, are the co-lead authors.

Other Stanford authors of the study are former Stanford postdoctoral scholar Benjamin Grewe, PhD; and research scientist Dong Wang, PhD.

Hanae Armitage is a science writer for the Stanford medical school's Office of Communication & Public Affairs. Her email is harmitag@stanford.edu.

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