Methcathinone Exposure Alters Host Behavior and Gut Microbiota Community in Zebrafish: A Microbiome-Metabolism-Behavior Axis in Forensic Toxicology

Background Methcathinone (MCAT), a synthetic cathinone of abuse, causes neurobehavioral toxicity, yet the involvement of gut microbiota and host metabolic reprogramming remains unknown, hindering forensic biomarker discovery. Methods Zebrafish were exposed to MCAT (1.0–10.0 µg/mL, 15 days). Behavioral phenotyping, 16S rRNA sequencing, PICRUSt2-based metabolic prediction, and intestinal histopathology were performed. Results MCAT induced dose-dependent behavioral deficits: hyperlocomotion, aggression, social impairment, anxiety. It reduced gut microbial α-diversity, depleted beneficial genera ( Lactobacillus , Parabacteroides ), enriched Tardiphaga / Sphingomonas , and caused intestinal inflammation. PICRUSt2 predicted reprogramming of relaxin, parathyroid hormone, and GnRH signaling pathways, which correlated with behavioral changes. Conclusion Chronic MCAT exposure reshapes gut microbiota and host metabolism, driving neurobehavioral toxicity via a microbiota-metabolism-behavior axis, offering candidate forensic biomarkers.