Tryptophan has been reported to enhance the ability of the microbial collective to protect the host against enteric pathogens by activating recombinant dopamine receptor D2 (DRD2) and its downstream pathways, thereby improving gut health and treating severe gastroenteritis, enterocolitis, hemorrhagic diarrhea, and acute kidney failure caused by certain intestinal pathogens [28]. This evidence concerns the gene DRD2 and gastroenteritis.