Intestinal bacteria of the genus Lactobacillus develop stress resistance and masculinity

Intestinal bacteria of the genus Lactobacillus interfere with the behavior and physiology of the brain of mice, making their hosts more cold-blooded, courageous and stress-resistant.

The composition of the microflora of the gastrointestinal tract includes hundreds and hundreds of species. The usual help in digesting food is not limited to their work, and scientists are only beginning to understand how diverse the influence of all these microorganisms is on our physiology. As has been shown in recent years, microflora in some way affects even the psychology and behavior of the host, and it happens either through secreted toxins or through stimulation of the immune system. However, studies devoted to this exciting topic are not yet enough to assert here something definite.

Scientists from University College in Cork (Ireland), along with colleagues from the University of McMasters (Canada), checked how changes in the composition of the intestinal microflora affect the behavior of mice.

Researchers fed the animals with broth containing Lactobacillus rhamnosus. Lactobacilli are friendly to the owners, they are the main ingredient in food additives, probiotics, but the possible side effects of their activity have not been studied. The experiment showed the effect of Lactobacillus rhamnosus on the behavior of animals, but it was in all senses positive. Mice, which for six weeks received a portion of bacteria with food, showed increased stress resistance and reduced anxiety in behavior. Animals spent more time exploring open spaces and narrow open "bridges", which usually inspire fear. When mice fed a bacterium were placed in water, the level of stress hormones they had less than other relatives in a similar situation.

Lactobacillus rhamnosus made rodents more cold-blooded and courageous, reducing the level of anxiety and stress.

As the researchers write in the journal PNAS, at the molecular level in mice with lactobacillus, features in the activity of genes encoding GABA receptors were noted. GABA (gamma-aminobutyric acid) is one of the main neurotransmitters in the brain; for nerve cells, it's something like a calming, activity-reducing, nervous neuron. Many drugs for the treatment of post-traumatic syndrome or panic attacks are aimed specifically at the cellular receptors of gamma-aminobutyric acid. The rearrangement of GABA receptors in the brain of mice with Lactobacillus rhamnosus was carried out in a rather complicated manner, in some areas of the brain of the receptors there was more, in some areas less, but as a whole, as the authors of the article emphasize, the changes led to a decrease in the level of anxiety in animals.

All these effects, apparently, are carried out by means of a vagus nerve, which collects information about internal organs and transmits it to the brain. If the mice cut the part that innervates the intestine, there was no difference between the mice with the bacterium and without it. However, how exactly Lactobacillus rhamnosus "communicates" with the vagus nerve, scientists can not yet say.

On the one hand, this is a remarkable study, addressed to the non-obvious aspects of our relationship with our own symbionts. On the other hand, is it possible to consider the effect that the bacterium Lactobacillus rhamnosus exerts on mice is so positive? After all, an overly brave mouse very quickly turns into a dead mouse. Finally, with great caution should spread the results to a person, yet our emotional life and our anxieties are more complex than mouse stresses ...

[1], [2], [3]