The Way to a Mouse's Brain Is Through its Stomach

Most researchers says that there are "open lines of communication" between the brain and the bowels, and that in mice, this line allows an individual's gut bacteria to influence behavior, says Not Exactly Rocket Science's Ed Yong. A new study published in PNAS solidifies the evidence for the "gut-brain axis," he adds. Researchers at University College Cork fed mice with Lactobacillus rhamnosus, the probiotic found in many dairy products, and found that the increased levels of probiotics changed the levels of signaling chemicals in the animals' brains, reducing behavior associated with stress and anxiety. "Probiotic bacteria — those that benefit their host — are the subject of sweeping, hand-waving health claims. But beneath the breathless marketing hype, there is some intriguing underlying science," Yong says. "For example, some trials have found that probiotics can help to alleviate the mood symptoms that accompany irritable bowel or chronic fatigue syndrome." The UCC researchers found that their probiotic mice were more likely to spend time in the exposed parts of their maze, suggesting they had less anxiety than other mice, and were also less likely to drift motionlessly when dropped in water, showing that they were not depressed. The bacteria also boosted GABA levels. That doesn't mean that eating lots of yogurt will cure your depression, Yong says, and it's not even clear if the gut-brain relationship in mice can be applied to humans. But this study does provide evidence that such trials should be extended to humans, he adds.