BDNF and Anxiety: In this study, we found that chronic ketamine exposure for 28 days caused gut microbiota dysregulation, reduced the expression of SCFAs in serum, hippocampus, and feces, elevated gut permeability, downregulated the BDNF-TrkB-ERK1/2-CREB signaling pathway, caused neuronal damage, and decreased the expression of synaptic proteins Syn and PSD-95, which may lead to anxiety-like behaviors, prepulse inhibition (PPI) deficits, and spatial learning and memory deficits.