Possible impact of the gut microbiota on the excitability of the brain

It is becoming increasingly evident that the role of the gut microbiota (GM) is not limited by the walls of the gastrointestinal tract (supporting the digestion, absorption of nutrients, intestinal motility and resistance to pathogens), but it also influences normal physiology of the whole organism and contribute to the broad range of diseases including those affecting the central nervous system (CNS). The growing appreciation of the role of intestinal bacteria in brain physiology has led to the establishment of so called \u201cgut-brain axis\u201d, or the \u201cmicrobiota-gut-brain axis\u201d, a bidirectional communication network between the gut and the brain. We hypothesized that gut microbiota form subjects affected by neural pathology can modulate in healthy subjects excitability in CNS and, finally, positively correlate with the level of seizure activity. The data obtained in this study suggests that mice received \u201cpro-pathological\u201d microbiota have compromised brain excitability. Microbiota composition of the donors with induced temporal lobe epilepsy (TLE) was characterized by the increase in Sutterella, Prevotella, Dorea, Coprobacillus and Candidatus Arthromitus in comparison with the baseline. These alterations, through the GBA, may possibly have an effect on the excitability of the brain and subsequently on the threshold for the seizure activity

Gut microbiota modulates seizure susceptibility

A bulk of data suggest that the gut microbiota plays a role in a broad range of diseases, including those affecting the central nervous system. Recently, significant differences in the intestinal microbiota of patients with epilepsy, compared to healthy volunteers, have been reported in an observational study. However, an active role of the intestinal microbiota in the pathogenesis of epilepsy, through the so-called "gut-brain axis," has yet to be demonstrated. In this study, we evaluated the direct impact of microbiota transplanted from epileptic animals to healthy recipient animals, to clarify whether the microbiota from animals with epilepsy can affect the excitability of the recipients' brain by lowering seizure thresholds. Our results provide the first evidence that mice who received microbiota from epileptic animals are more prone to develop status epilepticus, compared to recipients of "healthy" microbiota, after a subclinical dose of pilocarpine, indicating a higher susceptibility to seizures. The lower thresholds for seizure activity found in this study support the hypothesis that the microbiota, through the gut-brain axis, is able to affect neuronal excitability in the brain