In rats, anxiety isn’t all in the head. it can start in the heart

When you are stressed and anxious, you can feel your heart pounding. Is your heart racing because you’re scared? Or is your pounding heart contributing to your anxiety? Both may be true, a new study in rats suggests.

Scientists were able to artificially increase the heart rate of rats increase anxiety-like behavior — those whom the team silenced by turning off a specific part of the brain. The study, published March 9 Nature, shows that in high-risk contexts, a pounding heart can go to your head and increase anxiety. The findings may provide a new angle for studying and potentially treating anxiety disorders.

The idea that body sensations can contribute to emotions in the brain goes back at least to one of psychology’s founders, William James, says Carl Deisseroth, a neuroscientist at Stanford University. in James’s 1890 book principles of psychology, he put forward the idea that emotion follows the experiences of the body. James wrote, “We are sad because we cry, angry because we attack, afraid because we tremble.”

The brain can certainly sense internal body signals, a phenomenon known as interoception. But whether those sensations — like a racing heart — can contribute to emotion is difficult to prove, says Anna Belair, a neuroscientist at the French National Institute of Health and Medical Research in Bordeaux. She studies brain circuitry related to emotion and wrote a commentary on the new study but was not involved in the research. “I’m sure a lot of people thought about doing these experiments, but nobody really had the equipment,” she says.

Deisseroth has spent his career developing those tools. he is one of the scientists who developed optogenetics – a technique that uses viruses to modify the genes of specific cells burst of light response ,Sn: 6/18/21, Sn: 1/15/10, Scientists can use the flip of a light switch to activate or suppress the activity of those cells.

In the new study, Deisseroth and his colleagues used a light attached to a tiny vest on the genetically engineered heart of a mouse to alter the animal’s heart rate. When the light was off, a mouse’s heart pumped at a rate of about 600 beats per minute. But when the team turned on a light that flashed at a rate of 900 beats per minute, the mice’s heartbeats followed suit. “It’s a nice proper acceleration, [one a mouse] Encounters will occur in times of stress or fear,” Deisseroth explains.

When the rats felt that their heart was beating, they showed anxiety-like behavior. In risky scenarios—such as open areas where a small mouse could be someone’s lunch—rodents tend to lurk in dark corners along walls. When pressing a lever for water, which can sometimes be combined with a mild shock, rats with normal heart rates still pressed without hesitation. But the fast-hearted rats decided that they would stay thirsty.

“Everyone was expecting it, but this is the first time it has been clearly demonstrated,” says Belair.

The researchers also scanned the animals’ brains to locate areas that might be processing the increased heart rate. One of the biggest cues, Deisseroth says, came from posterior insula ,Sn: 4/25/16, “The insula was interesting because it is highly associated with interoceptive circuitry,” he explains. “When we saw that sign, [our] Interest was certainly piqued.

Using more optogenetics, the team reduced activity in the posterior insula, which led to a decrease in the mice’s anxiety-like behavior. The animals’ hearts were still racing, but they behaved more normally, spending some time in the open areas of the maze and pressing the lever for water without fear.

A lot of people are very excited about the work, says Wayne Chen, branch chief of basic medical research for complementary and integrative health at the National Center for Complementary and Integrative Health in Bethesda, MD. In the past two days, everyone brought up this paper,” says Chen, who was not involved in the research.

The next step, Deisseroth says, is to look at other parts of the body that can affect anxiety. “We can feel it in our gut sometimes, or we can feel it in our neck or shoulders,” he says. Using optogenetics to stress a mouse’s muscles, or giving them stomach butterflies, may reveal other pathways that produce fearful or anxiety-like behaviors.

Understanding the link between the heart and the head may ultimately factor into how doctors treat panic and anxiety, Bayler says. But the path between lab and clinic, she notes, is far more complex than that from heart to head.