1. Introduction
2. SSRIs are antimicrobial
3. SSRI dysbiosis: potential link to loss of sexual desire
4. Why do SSRIs modulate the gut microbiome?
5. Conclusions
6. Article Summary
7. References
8. Related Articles

Introduction

The ‘Gut’ is the informal term for the gastrointestinal tract, primarily responsible for nutrient absorption and separation from waste. Many people, perhaps the majority, would consider this as being the sole purpose the gastrointestinal tract – but recent scientific developments have shone light onto a whole new function of the gut.

As it turns out the gut is intimately interconnected to the brain in what’s now called the ‘gut-brain’ axis. People may be familiar with the influence of emotional states over digestion, particularly in the context of stress, however this axis is a two-way street.

Suganya, Kanmani, and Byung-Soo Koo, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons

Changes to the composition of the gut microbiota or the structure of the gut can have a profound influence over the brain. One of the more direct ways by which the gut can influence brain activity is through the synthesis and absorption of metabolites of neurotransmitters (such Tryptophan Indoles) and their precursors (phenylalanine) which then cross the blood barrier to influence concentrations of dopamine, serotonin, and GABA. [1][20]

This isn’t an insignificant contribution either, with more than 50% of dopamine in the body being synthesised in the gut. [2] The neurotransmitters produced by the gut serve both to gastrointestinal functions like motility, as well as send signals directly to the brain through the vagus nerve.

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