2024-01-11 14:00:00
An Inserm team suspects the vagus nerve, which connects the brain to the intestines, of playing a role in the development of depression.
It is the most extensive nerve in the body. The vagus nerve starts from the brain and links it to several organs including those of the digestive system. Researchers believe thatit might play a role in depression, by linking mental illness with the intestinal microbiota.
Various studies have shown that depression is linked to the composition of the intestinal flora. First, depressed people have an altered microbiota, that is to say with a deficit or excess of bad bacteria. Secondly, if we transfer the microbiota of an individual suffering from depression to a healthy being, the latter develops the same disease. Which confirms the causal link. ButScientists still cannot fully understand what is happening in these organisms, and why bad bacteria manage to create a depressive state.
Bacteria impact the vagus nerve
In a article scientific published in May 2023, a team from Inserm studied a path : the vagus nerve. This last “connects the brain to different organs including the digestive system and thus constitutes a direct anatomical link between the two”explains Eleni Siopi, first author of this work, in a recent press release. “Furthermore, intestinal bacteria are found near this nerve and impact its activity. And this nerve is connected to brain regions involved in managing emotions.”
The researchers tested this hypothesis on mice in good health. Some had an intact vagus nerveothers had one severed at the level of the abdomen. What the scientists did is simple: they transferred an altered microbiota from organisms that suffered from depression to rodents of the two groups. “This transfer procedure is common in the laboratory to induce depression in recipient animals. This is explained by a loss of interest, of curiositymotivation, or even apathy during simple exercises”specifies the author.
Results : mice with an intact vagus nerve showed these depressive symptomswhile those with a severed nerve remained mentally healthy.
“The effect is very significant since all of the animals concerned were protected from the disease. Vagotomy (section of the vagus nerve, editor’s note) caused a decoupling of the intestine and the brain which was enough to preserve subjects from a depressive state Provoked by” an intestinal imbalance, she presents.
Stimulating the vagus nerve, the treatment of tomorrow?
These results allow us to know more regarding this link between microbiota and depression, but above all they might open up some avenues for reflection on future treatments. The disease is currently poorly cared for by current treatments: approximately 30% of patients do not respond satisfactorily to serotonin reuptake inhibitors, and suffer from resistant depression.
The idea would be to offer, alongside treatments, vagus nerve stimulation therapies with meditation or massagesconcludes the scientist.
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