Scientists have found a way to “turn off” anxiety by targeting cells in the brain

If you’ve ever suffered from anxiety, even in its mildest forms, you’ll be familiar with the feeling of elevated heart rate, sweaty palms and panic.

While the sources of anxious behaviours have previously been plotted across the brain, researchers now believe they’ve uncovered the cells responsible for creating this anxious state in the first place. 

Neuroscientists at Columbia University Irving Medical Center (CUIMC) and the University of California, San Francisco (UCSF) said cells in the brains of mice, spotted inside the hippocampus, only fire when the animals are in places that are “innately frightening” to them, such as open areas where they feel more exposed, or high up on a platform. 

 The hippocampus has long been known to play a role in the brain’s ability to form new memories and to help animals make their way through new and complex environments, yet recent research has suggested the hippocampus regulates mood. Studies have shown altering brain activity in the ventral part of the hippocampus can reduce anxiety, plus it’s known that the hippocampus sends signals to other areas of the brain, such as the amygdala and the hypothalamus, believed to control anxiety-related behavior.

Using a miniature microscope inserted into the brains of the mice, Rene Hen, PhD, a professor of psychiatry at CUIMC and his team recorded the activity of hundreds of cells in the hippocampus as the mice moved around their surroundings.

Whenever the animals were in exposed, anxiety-provoking environments, the researchers spotted that specific cells in the ventral part of the hippocampus were active. And the more anxious the mice seemed, the greater the activity in these cells.

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The so-called “anxiety cells” are shown

The researchers traced the output of those cells to the hypothalamus, which is known to control behaviours associated with anxiety. In humans, such behaviours include increased heart rate, avoidance, and secretion of stress hormones. In mice, theu include avoiding a dangerous area or fleeing to safety. 

By turning the anxiety cells off and on using a technique called optogenetics, which lets scientists control the activity of neurons with beams of light, the researchers found that the anxiety cells control anxiety behaviours. When the cells were switched off, the mice stopped acting scared and wandered onto raised platforms and away from protective walls. When the cells were stimulated, the mice exhibited fled to “safe” surroundings.

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“This is exciting because it represents a direct, rapid pathway in the brain that lets animals respond to anxiety-provoking places without needing to go through higher-order brain regions,” said Mazen Kheirbek, PhD, an assistant professor of psychiatry at UCSF.

“Now that we’ve found these cells in the hippocampus, it opens up new areas for exploring treatment ideas that we didn’t know existed before,” says the study’s lead author Jessica Jimenez, PhD, an MD/PhD student at Columbia University’s Vagelos College of Physicians and Surgeons.

However, the researchers are keen to stress that a certain level of anxiety can be good for you.

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For example, anxiety is an “emotional response to a distant threat”, such as being in an environment that exposes an animal to predators. Anxiety kicks in to help them avoid the threat. It’s only when people overestimate threats, when talking to a crowd invokes the same response as potentially running into a snake, that anxiety becomes a problem.

The discovery of the anxiety cells raises the possibility of finding treatments that target them and reduce anxiety. “We’re looking to see if these cells are different molecularly from other neurons,” Hen said. “If there’s a specific receptor on the cells that distinguishes them from their neighbors, it may be possible to produce a new drug to reduce anxiety.”

The findings are published in journal Neuron

Images: Hen Lab/Columbia University/Shutterstock

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