It was also shown to block depression-like behaviors in Chrna7 knock-out mice (the gene coding for the α7 subtype of the nicotinic acetylcholine receptor), an animal model that demonstrates depression-like behaviors through abnormal composition of the GM and systemic inflammation [81], demonstrating the central role of the vagus nerve in the gut–microbiota–brain axis. This evidence concerns the gene CHRNA7 and major depressive disorder.