Fig. 1

The schedule of the experiments. a The schedule of treatment of antibiotic cocktail, fecal microbiota transplantation (FMT), collection of fecal samples, sucrose preference test (SPT), and collection of the plasma and brain. Antibiotic cocktail or water in drinking water was given to adult male mice for 14 days (day 1–day 14). Subsequently, FMT from CSDS-susceptible mice or control (no CSDS) mice was performed for 14 days (day 15–day 28). On day 29, fecal samples were collected. On day 30, 1% SPT was performed. On day 31, the plasma and brain (i.e., PFC) were collected. b The schedule of treatment of antibiotic cocktail, microbiota transplantation, collection of fecal samples, behavioral tests, and collection of the plasma and brain. Antibiotic cocktail or water in drinking water was given to adult male mice for 14 days (day 1–day 14). Subsequently, two bacteria (L. intestinalis and L. reuteri) were administered orally for 14 days (day 15–day 28) using gastric gavage. On day 29, locomotion test (LMT) and tail suspension test (TST) were performed. Forced swimming test (FST) and 1% SPT were performed on days 30 and 31, respectively. On day 32, the plasma and brain were collected. c The schedule of subdiaphragmatic vagotomy (SDV), treatment of antibiotic cocktail, microbiota transplantation, behavioral tests, and collection of the plasma and brain. SDV or sham was performed in adult male mice, and mice were recovered 14 days after surgery (day 1–day 14). Subsequently, an antibiotic cocktail or water in drinking water was given to all mice for 14 days (day 15–day 28). Subsequently, transplantation of two microbiota was performed for 14 days (day 29–day 42). On day 43, LMT and TST were performed. FST and 1% SPT were performed on day 44 and day 45, respectively. On day 46, the plasma and brain were collected