What is already known on this topic
Changes in gut microbiota composition can modulate behaviors such as social activity, stress, and anxiety, which are associated with neuropsychiatric disorders. But little is known about the mechanisms through which gut bacteria influence the brain.
What this research adds
Researchers trained mice to connect a tone with an electric shock, and measured for how long the rodents associated the noise with pain. Mice with normal microbiota eventually forgot the connection, whereas those with a disrupted microbiota showed persistent fear. By analyzing the brains of the mice, the researchers found differences in brain regions associated with fear and learning. These differences appear to be a result of distinct levels of chemicals produced by gut microbes.
The results highlight the role of the microbiota in gut-brain communication and shed light on risk factors of conditions such as chronic anxiety and post-traumatic stress disorder.
The gut microbiota could help mice to shake off fearful memories, according to new research. The finding, published in Nature, suggests that gut bacteria play an important role in learning and forgetting, and could help understand conditions such as chronic anxiety and post-traumatic stress disorder.
Several behaviors such as social activity, stress, and anxiety—which are all associated with neuropsychiatric disorders—can be modulated by gut bacteria. But how exactly the microbiota influences the brain remains unclear.
To address this question, a team of researchers led by Coco Chu at Cornell University trained mice to connect a tone with an electric shock, and measured for how long the rodents associated the noise with pain.
After several sessions of hearing the tone but not getting the shock, mice with a normal microbiota forgot the association and didn’t display fearful behavior.
In contrast, rodents with a disrupted gut microbiota continued to show fear in response to the noise. The researchers observed the same behavior in mice that completely lacked gut microbes.
When the researchers looked at the mice’s brains, they found differences in gene activity in brain regions associated with fear and learning. These differences appear to be a result of distinct levels of four metabolites produced by the gut microbes.
Mice that lacked gut microbes had lower levels of these metabolites compared to those with a normal microbiota. These substances might help to forget fear, and two of them are associated with neuropsychiatric conditions such as schizophrenia and autism.
The results suggest that the microbiota can affect the brain through chemicals that are released into the bloodstream, and that targeting gut bacteria and their metabolites might be a strategy for helping people with conditions such as post-traumatic stress disorder, the scientists say.