The intestinal microbiota – known by all as intestinal microflora – plays a fundamental role in the development and maintenance of the function of the immune system and in the regulation of body weight. New studies suggest that the microbiota could also be involved in the communication pathway between the center and periphery called the gut-brain axis, modulating brain functions and ultimately our behavior.
To examine in detail the connection between microbiota and brain, Paola Tognini, researcher of the Department of Translational Research (Physiology Unit) of the University of Pisa, in collaboration with Tommaso Pizzorusso professor of the Scuola Normale Superiore and associate researcher of the Institute of Nurosciences of the Cnr of Italy (Pisa), have studied how signals coming from intestinal bacteria can influence neuronal plasticity. The study, entitled “The gut microbiota of environmentally enriched mice regulates visual cortical plasticity”, was published in the prestigious international scientific journal Cell Reports and is the result of a collaboration between the University of Pisa, Scuola Normale Superiore, Institute of Neuroscience of the Cnr, Stella Maris Foundation and University of Milan.
“Brain or neuronal plasticity is the ability of our brain to change in response to stimuli from the external environment and / or in response to our experiences. The brain is more plastic, and therefore prone to change during youth, while its circuits are more stable and therefore resistant to change during adulthood. In our study we tried to understand if signals coming from the intestinal microbiota could reactivate plasticity in the adult brain – explain Paola Tognini and Tommaso Pizzorusso – To achieve this goal, we used the visual system as a model, precisely because adult animals do not normally show plasticity in this area of the brain”.
The researchers raised the mice in a particular environment characterized by an increase in sensory and social experiences and which favors physical activity. These mice, defined as “enriched”, had a different microbiota from that of mice raised in classic laboratory cages and showed brain plasticity, as occurs in young animals. However, when these mice were deprived of their microbiota, the reactivation of neuronal plasticity was completely nullified, suggesting that signals from the gut were responsible for the effect. Finally, intestinal microbiota transfer via fecal transplantation from plastic-enriched mice to standard mice, which do not have plastic brains, caused an increase in neuronal plasticity in the recipient mice.
“Our study introduces a very new concept, namely that of the existence of a gut microbiota-brain experience connection: our experiences not only affect the brain directly but also through signals from our gut”.
The implication of the results achieved with this study is broad and not limited to the sensory systems and the visual cortex. In fact, research could open new frontiers to promote neuronal plasticity in neurodevelopmental or neurodegenerative diseases, based on therapeutic strategies aimed at modulating the gut-brain axis.