LPS injection caused increased turnover of TRP, 5-HT, and DA. CX3CR1+/- (Control) or CX3CR1-/- (KO) mice were injected i.p. with saline or LPS (0.5 mg/kg). Because there was no significant effect of genotype, data were collapsed to show the main effect of LPS. A) The ratio of KYN to TRP was determined in the brain and plasma 24 h later. B) The ratio of 5-HIAA to 5-HT, C) the ratio of HVA to DA, D) the ratio of DOPAC to DA were determined in the brain 24 h later. Bars represent the mean ± SEM. Means with * are significantly different (P < 0.05) from saline controls.