CHRNA7 and depressive disorder: One recent report indicated FMT from the α7 subtype of the nicotinic acetylcholine receptor knockout mice (Chrna7 KO mice) showed depression-like phenotypes treated with an antibiotic cocktail, while subdiaphragmatic vagotomy significantly blocked the development of depression-like phenotypes [74], it is possible that some metabolites of the Ri. may participate in stimulation of the vagal afferent nerves, modulating Trp-5-HT and Trp-Kyn metabolism in the brain.