In this study with citalopram hydrobromide (Sigma), four experimental groups were utilized: control with vehicle (CONV), control with citalopram (CONCIT), chronic social defeat with vehicle (CSDV), and chronic social defeat with citalopram (CSDCIT) (n=7 in each group). CSDCIT and CSDV were exposed to chronic social defeat protocol for 5 d, while CONCIT and CONV acted as the corresponding control group and underwent a similar procedure as the subject fish without the social defeat stress. On day 6 to day 10, CSDCIT and CONCIT were administered with citalopram (10 mg/kg body weight) in 40μL water via intraperitoneal injection. The dose for citalopram was determined based on the effective dose previously used in rodents (55 (link)) and SSRI treatment in zebrafish (56 (link)). CSDV and CONV were administered with water. Treatment continued for a period of 5 d. On day 10, the brain samples were collected 5 h after the last dose of citalopram (Fig. 3E). SPX1a gene expression analysis by quantitative real-time PCR was performed as described above.