ABSTRACT
Neuroscience and microbiology domains in modern life sciences have long developed along distinct routes, except for studies focused on the direct impact of infectious agents on brain function. However, it has recently become evident that microbiota, notably gut-microbiota, has a signifi cant impact on all aspects of human physiology, including gut-brain communication, brain function and behavior (Cryan and Dinan 2012). Both clinical observations and psychiatric co-morbidity in various chronic intestinal disorders (e.g., in the irritable bowel syndrome and infl ammatory bowel disorders) support the role of intestinal microbiota in gut-brain communication (Bercik et al. 2012). An increasing amount of experimental evidence on gut microbiome modulation of cognitive functions and stressrelated behaviors, such as anxiety and depression, has been reported, as well as a possible contribution to severe psychiatric disorders, such as
Email: roberto.mazzoli@unito.it
autism (Adams et al. 2011, Williams et al. 2011, Cryan and Dinan 2012). Experimental strategies, including the use of germ-free animals, animals infected with pathogenic bacteria and animals exposed to probiotic or antibiotic agents, have revealed a number of microbial effects on host health and behavior (Cryan and Dinan 2012). The concept of a microbiota-gut-brain axis has therefore emerged as an extension of the well established gut-brain bidirectional homeostatic route of communication. This interactive network consists of: i) a multiple mechanism interaction between the heterogeneous microbiota and the gut; ii) multiple pathway communication, i.e., through immune, neural and endocrine signaling, between the intestinal tract and the central nervous system. Because of its great complexity, it is hard to dissect the microbiota-gut-brain axis into its distinct constituents. The keys to understanding the observed macroscopic effects at the molecular level are therefore far from being completely understood. The following sections will attempt to provide state-of-the-art knowledge on the mechanisms by which gut microbiota can infl uence gut-brain communication, thus supporting the use of probiotic strains as potential therapeutic agents in neuro-enteric disorders, starting with a brief description of the gut-brain axis.
