2024-01-02 16:01:00
What if the vagus nerve connecting the brain to the gut was the cause of depression? The question is seriously asked by French researchers.
The link between depression and dysfunction of the intestinal microbiota has already been widely studied. Patients suffering from this mental illness have, according to various previously published studies, abnormalities in the composition of their intestinal flora. In particular, they present an imbalance of bacteria naturally colonizing the entire digestive system. The proof is: the transfer of intestinal microbiota cells taken from a depressed patient is enough to trigger this disease in a “healthy” patient.
But which part of the body connecting the brain to the intestine might be affected? According to researchers from Inserm, the Pasteur Institute and the National Center for Scientific Research (CNRS), the vagus nerve, the largest in the human body, connecting the intestine and the brain would be able to “condition the occurrence of depression induced by abnormalities of the intestinal microbiota”.
Uncoupling the gut from the brain
“Intestinal bacteria are found near this nerve and impact its activity,” underlines Professor Eleni Siopi (Paris Cité University), first author of this work. And this nerve is connected to brain regions involved in managing emotions. “
To study the role of the vagus nerve in depression, the researchers “carried out transfers of microbiota from mice suffering from this disease to other, healthy ones, presenting an undamaged vagus nerve or, on the contrary, severed in the abdomen (vagotomy). )”. So how can we spot depressed mice? This results in a loss of interest, curiosity, motivation, or even apathy during simple exercises.
Symptoms observed in mice in the control group, therefore initially presenting an uninjured vagus nerve. On the other hand, in rodents whose vagus nerve was cut, “the transfer of microbiota did not induce depression”. Results: “vagotomy caused a decoupling of the intestine and the brain which was sufficient to preserve the subjects from the depressive state caused by intestinal dysbiosis,” clarifies the researcher.
Meditation and massage
Identifying the vagus nerve as the seat of depression can already be of use to patients suffering from depression, by acting at this precise level. “Stimulating the vagus nerve through meditation or even massages might strengthen the effect of treatments thanks to better stress control.
In addition, modulating the activity of specific proteins or molecules of the vagus nerve might help fight once morest the severity or recurrence of depression in patients”, hopes Eleni Siopi. A priority because at “currently, only a third patients are effectively relieved by medications, which means that additional solutions are expected,” she concludes.
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