In our cefaclor-induced anxiety and depression-like symptoms, even though there is a need to further investigation of the interaction between BDNF and serotonin signaling via the vagus nerve, vagotomy prevented the reduction of BDNF levels in the hippocampus of cefaclor-fed vagotomized mice compared with cefaclor-fed sham-operated mice. Here, BDNF is linked to major depressive disorder.