Scientists released a caged rat into the forest, a surprising thing happened

Dozens of lab mice allowed to roam a large outdoor enclosure returned to normal levels of mouse anxiety after a week, the researchers observed, suggesting that ‘rewilding’ may prevent lab-induced fear responses from developing in the first place.

Researchers at Cornell University in the US say their findings raise questions about the best ways to conduct anxiety tests in laboratory animals. It can also teach us something about how anxiety begins in animals, including us.

“We put them in the field for a week, and they returned to their original level of anxiety behavior,” says biologist Matthew Zipple.

“Living in this natural environment both inhibits the formation of the initial fear response, and it can reset the fear response that has already developed in these animals in the laboratory.”

Related: Scientists identify the neurons that drive anxiety — and how to calm them

Researchers typically induce and measure anxiety in rats using what is known as the elevated plus maze or EPM. It has two arms: a closed arm, which makes the animals feel safe, and an open arm, where the rats are in a more open environment.

In a standard response to EPM, rats seek to explore the maze before returning to the closed spaces. It is interpreted as a sign of fear triggered by a single exposure to open areas, a behavior so persistent that it resists SSRI anti-anxiety drugs.

When the researchers released 44 rats from their lab cages to explore a relatively large space outside, burrow and climb, and experience different sensations and situations, they found it acted like a reset button.

Rats returning to the EPM explored both the open and closed spaces equally as if they had encountered the maze for the first time. The effects were observed in mice whether they were resuscitated from birth or not.

This may have consequences for how we perceive anxiety and its relationship to our environment—something that may also be true in humans and rodents. It is possible that a narrow set of experiences can increase anxiety.

Related: Anti-anxiety ‘chill-out drinks’ are taking the market by storm. Are they safe?

“If you experience a lot of different things that happen to you every day, you have a good way of calibrating whether something is scary or scary,” says neurobiologist Michael Sheehan.

“But if you’ve only had five experiences, you come to your sixth experience, and it’s so different from anything you’ve had before, it’s going to cause anxiety.”

The researchers suggest that there may be a need to rethink how anxiety is studied in the lab, and how experiments with mice can be applied to humans. What we think of as anxiety in laboratory rats is easily mitigated by their environment rather than being hardwired into their biology.

This idea of ​​a more sheltered life as a contributor to anxiety is something that has also been explored in studies of individuals. Perhaps more varied and more risky experiences can help reduce anxiety – although we also know that there are many factors involved.

Related: The roots of your anxiety may go back to a time before you were born

“It opens up a lot of possibilities for asking interesting questions about how our library of experiences shapes our response to novel experiences, because I think that’s what anxiety is — when you have an inappropriate response to something that’s not actually scary,” Sheehan says.

Research has been published in Current Biology.

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