Friendly Bacteria Cheer Up Anxious Mice
A happy stomach leads to a happy mood? While some of us may have already experienced the wonders of a full stomach, these neuroscientists have shown why that is.
Most everyone knows that stress can cause a clenched, gurgling, unhappy stomach. What’s less well known is that the relationship goes both ways.
Beneficial gut bacteria, or probiotics, have been shown in the past to alleviate symptoms of stress and anxiety, but it wasn’t clear whether the bugs could have an impact on the brains of healthy animals. Now, John Cryan, a pharmacologist with the Alimentary Pharmabiotic Center at University College Cork, Ireland, and colleagues have found that probiotics have a direct impact on mood neurotransmitters in mice1. The findings further support the idea that one way to heal problems of the mind might be through the stomach.
Cryan’s group fed a strain of Lactobacillus rhamnosus — a species found in some yoghurts — to 16 healthy mice. The dose they used was roughly the same as the amount of probiotic cultures claimed to be in a pot of Actimel yoghurt.
The team then ran the mice, along with 20 mice fed a bacteria-free broth, through a battery of stress tests. In negotiating a maze, the mice that received probiotics ventured out into open spaces more than twice as often as the control mice, suggesting that they were less anxious. And when forced to swim, the bacteria-fed mice were slightly more prone to struggle — rather than give up — than their broth-fed brethren. “These mice were more chilled out,” says Cryan, adding that the effects of the probiotics were similar in magnitude to those seen in mice for antidepressant drugs. Cryan and his colleagues report their results in Proceedings of the National Academy of Sciences this week.