This article is from the public number: Neural Reality (ID: neureality) , author: ELENA RENKEN, Quantamagazine internship writer, science writer, now living in New York. Former editor of the Brown Daily Herald at Brown University, and a bachelor’s degree in science, technology, and society from Brown University. Translation: Pocket Worm, Proofreading: Selflessness
Gut flora and our fears
From a physiological point of view, our brain seems to be far from the gut. However, recent research has strongly pointed out that the large number of bacteria clustered in our digestive tract opens up communication channels between the brain and the intestine. The intestinal flora has been proven to act on the host’s emotional, emotional, mental illness, and even information processing processes. But how the flora does this has been elusive.
So far, most studies on the gut-brain relationship have only pointed out the correlation between the flora status and brain activity. The new findings are based on the study of the flora’s involvement in the stress response, trying to drill deeper. Now researchers are focusing on fear, and especially how it fades over time. They tracked behavioral changes in mice with reduced flora and found abnormalities in cell connectivity, brain activity, and gene expression.
Researchers have also discovered a short window period for newborn mice. If the flora in the mice returns to normal during this window period, they can avoid behavioral defects in adulthood. They even tracked four special compounds that might help explain these changes. If we can understand the relationship between the intestinal flora and the brain, we can predict which treatments should be used in the future. Although it’s too early to talk about this, the differences found in the study clearly confirm the close relationship between the gut and the brain.
— Eoin Ryan
University of Colorado Boulder, Associate Professor of Integrated Physiology, Christopher Lowry (Christopher Lowry) said that determining the interaction between the intestinal flora and the brain The mechanism of action is a major challenge for microbial research. “At the moment we have some clues,” he added.
How does flora interact with the brain?
Coco Chu, lead author of mouse research and postdoctoral fellow at Will Cornell University School of Medicine (Coco Chu) The idea that bacteria in the body may affect our feelings and behavior is of interest. With the help of psychiatrists, microbiologists, immunologists, and scientists in other fields, she began exploring the interactions in detail a few years ago.
Researchers performed classic behavioral training on mice. Some of these mice were injected with antibiotics, which caused them to rapidly reduce their flora. Others were fed under isolation and had no flora at all. All mice learned well at the stage of using electric shock to train mice to fear a certain sound.
After the researchers removed the shock, mice with normal flora gradually learned to stop fearing the sound. And those mice with a slump of bacteria and a germ-free group have a persistent fear reaction, and they are more likely to have a rigid response when they hear this sound.
Researchers have found that the medial prefrontal cortex of mice lacking the flora is (responsible for processing fearThe outer brain region of the fear response) showed significant differences: the expression of some genes was reduced; a glial cell failed to develop normally; the number of spinous processes associated with learning on neurons was less and more prone to apoptosis; A cell has a low level of neural activity. Mice lacking a healthy flora seem to be able to eliminate fear, which can also be observed at the cellular level.
Researchers are also beginning to explore how the state of the intestinal flora can cause these changes. One possible explanation is that bacteria send signals to the host’s brain through the long vagus nerve (long vagus nerve) . The vagus nerve is mainly responsible for transmitting the feelings of the digestive tract to the brain stem. However, cutting the vagus nerve did not change the behavior of the mice. Another possible explanation is that the flora stimulates the immune system’s response, which affects the host brain. However, the number and proportion of immune cells in each group of mice were very close.
The researchers did pinpoint one point: there are differences in four neurologically active metabolites in different groups of mice. These substances are low in serum, cerebrospinal fluid, and feces in mice lacking the flora. Some compounds have been linked to neurological diseases in humans. According to David Addis, a microbiologist, senior author in this study, and director of the Gilbert Roberts Institute for Inflammatory Bowel Disease at Will Cornell Medical College (David Artis) said the research team speculated that the flora may secrete a large number of substances, some of which will enter the host brain.