Researchers Discover 'Anxiety Cells' In The Brain

Jan 31, 2018
Originally published on February 1, 2018 8:02 am

Scientists have found specialized brain cells in mice that appear to control anxiety levels.

The finding, reported Wednesday in the journal Neuron, could eventually lead to better treatments for anxiety disorders, which affect nearly 1 in 5 adults in the U.S.

"The therapies we have now have significant drawbacks," says Mazen Kheirbek, an assistant professor at the University of California, San Francisco and an author of the study. "This is another target that we can try to move the field forward for finding new therapies."

But the research is at an early stage and lab findings in animals don't always pan out in humans.

The discovery of anxiety cells is just the latest example of the "tremendous progress" scientists have made toward understanding how anxiety works in the brain, says Joshua Gordon, director of the National Institute of Mental Health, which helped fund the research.

"If we can learn enough, we can develop the tools to turn on and off the key players that regulate anxiety in people," Gordon says.

Anxiety disorders involve excessive worry that doesn't go away. These disorders include generalized anxiety disorder, panic disorder and social anxiety disorder.

Kheirbek and a team including several researchers from Columbia University discovered the cells in the hippocampus, an area of the brain known to be involved in anxiety as well as navigation and memory.

They did it by studying some anxious mice, Kheirbek says. "Mice tend to be afraid of open places," he says. So the team put mice in a maze in which some pathways led to open areas. Then the researchers monitored the activity of brain cells at the very bottom of the hippocampus.

"And what we found is that these cells became more active whenever the animal went into an area that elicits anxiety," Kheirbek says.

This activity didn't prove the cells were causing anxious behavior, though. So the team found a way to control the activity of these cells using a technique called optogenetics.

The team set out to answer a simple question, Kheirbek says:

"If we turn down this activity, will the animals become less anxious? And what we found was that they did become less anxious. They actually tended to want to explore the open arms of the maze even more."

When the researchers dialed up the cells' activity, the mice got more anxious and didn't want to explore at all.

But there's a lot more to anxiety than just these cells in the hippocampus, Kheirbek says. "These cells are probably just one part of an extended circuit by which the animal learns about anxiety-related information."

For example, the cells in the hippocampus communicate with another brain area called the hypothalamus that tells mice when to avoid something dangerous. Kheirbek says other parts of the anxiety circuit might detect dangerous odors or sounds.

"You can think of this paper as one brick in a big wall," Gordon says. In recent years, he says, scientists have been finding and assembling other bricks at rapid pace.

And they need to because anxiety disorders are "incredibly prevalent," Gordon says. "They hit us in the prime working years of life, and our treatments are, at best, partially efficacious."

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RACHEL MARTIN, HOST:

Scientists have identified specific brain cells that appear to control anxiety in mice. This could have implications for treating people with debilitating anxiety. Here's NPR's Jon Hamilton.

JON HAMILTON, BYLINE: There's a part of the brain that plays a key role in anxiety. It's called the hippocampus, and scientists wanted to learn more about precisely what the hippocampus is doing. So a team that included Mazen Kheirbek of the University of California, San Francisco studied the brains of mice. Kheirbek says they're great for this kind of experiment because they lead anxious lives.

MAZEN KHEIRBEK: Mice tend to be afraid of open places. So, for example, if you have a mouse in your apartment, the mouse will kind of run along the walls and won't really enter into the center of the room.

HAMILTON: To mimic that situation in the lab, the team put mice in a maze in which some pathways lead to scary, open spaces. Then they monitored the activity of brain cells at the very bottom of the hippocampus.

KHEIRBEK: And what we found is that these cells became more active whenever the animal went into an area that kind of elicits anxiety in these animals.

HAMILTON: That didn't prove the cells were causing anxious behavior though, so the team found a way to control the activity of these cells. Kheirbek says they wanted to answer a simple question.

KHEIRBEK: If we basically turned down this activity, will the animals become less anxious? And what we found is that they did become less anxious. They actually tended to want to explore the open arms of the maze even more so.

HAMILTON: When the researchers dialed up the activity, the mice got more anxious and didn't want to explore at all. But Kheirbek says there's a lot more to anxiety than just these cells in the hippocampus.

KHEIRBEK: These cells are probably just one part of an extended circuit by which the animal learns about anxiety-related information.

HAMILTON: For example, the cells communicate with another brain area that tells mice when to avoid something dangerous. Kheirbek says other parts of the anxiety circuit might detect dangerous odors or sounds. The team published their findings in the journal Neuron. And Joshua Gordon, who directs the National Institute of Mental Health, says it's an important advance.

JOSHUA GORDON: You can think of this paper as one brick in a big wall.

HAMILTON: Gordon says scientists are finding and assembling other bricks in the anxiety wall at a rapid pace. And they need to, he says, because nearly 1 in 5 adults in the U.S. suffers from an anxiety disorder, like out of control worrying, panic attacks or social phobia.

GORDON: Anxiety disorders are incredibly prevalent. They hit in the prime working years of life, and our treatments are, at best, partially efficacious.

HAMILTON: Gordon says treatments that specifically target the anxiety circuit should work better.

GORDON: If we can learn enough, we can develop the tools to turn on and off the key players that regulate anxiety in people.

HAMILTON: Gordon says that's why his institute is funding a wide range of research on anxiety, including the work that led to this new study.

Jon Hamilton, NPR News.

(SOUNDBITE OF HYAKKEI'S "PAVEMENT ALONG THE GINKGO TREES") Transcript provided by NPR, Copyright NPR.