Gut Bacteria Produce Brain-altering Drugs
All of the above are neurotransmitters/hormones already normally employed. Also, more is not necessarily better. I think they’re all somewhat common in our guts (I didn’t verify all of them). I don’t know whether a course of antibiotics completely eradicates gut bacteria (I’m guessing not), but presumably you’ll end up hosting some population or another absorbed from ingestion or respiration, even if your gut is briefly sterilized. (not all streptococcus species are “strep throat”-harmful) HTLyte lists these neurochemicals produced by various microbial species:
Lactobacillus, Bifidobacterium GABA Escherichia, Bacillus, Saccharomyces Norepinephrine Candida, Streptococcus, Escherichia, Enterococcus Serotonin Bacillus, Serratia Dopamine Lactobacillus Acetylcholine