o Which are the specific steps of 5-HT metabolism that are affected by the microbiota? o TPHl: the rate-limiting enzyme for 5-ht biosynthesis in ECS O SLC6A4: 5-hT transporter Which are the specific steps of 5-HT metabolism that are affected by the microbiota?  TPH1: the rate-limiting enzyme for 5-HT biosynthesis in ECs  SLC6A4: 5-HT transporter