Microbiota and Pain: Save Your Gut Feeling

Abstract

Recently, a growing body of evidence has emerged regarding the interplay between microbiota and the nervous system. This relationship has been associated with several pathological conditions and also with the onset and regulation of pain. Dysregulation of the axis leads to a huge variety of diseases such as visceral hypersensitivity, stress-induced hyperalgesia, allodynia, inflammatory pain and functional disorders. In pain management, probiotics have shown promising results. This narrative review describes the peripheral and central mechanisms underlying pain processing and regulation, highlighting the role of the gut-brain axis in the modulation of pain. We summarized the main findings in regard to the stress impact on microbiota's composition and its influence on pain perception. We also focused on the relationship between gut microbiota and both visceral and inflammatory pain and we provided a summary of the main evidence regarding the mechanistic effects and probiotics use.

Keywords: gut-brain axis; microbiota; pain; probiotics.

Figure 1

Schematic representation of the microbiota-gut-brain axis. The gut microbiota signals to the enteric nervous system (ENS) and to the CNS via different pathways, including endocrine, immune, metabolic and neuronal pathways as described throughout the text. In physiological conditions, the blood-brain barrier (BBB) allows the access of tryptophan metabolites and SCFAs into the CNS but blocks the passage of circulating neurotransmitters except for gamma aminobutyric acid (GABA). However, in pathological conditions, the disruption of BBB leads to an increased amount of circulating neurotransmitters in the brain.