Upregulation of neuronal kynurenine 3-monooxygenase mediates depression-like behavior in a mouse model of neuropathic pain.

•Nerve injury induces depression and upregulates kynurenine 3-monoxygenase (KMO) expression and activity.•KMO is upregulated in neurons in the contralateral hippocampus and not in microglia.•Upregulation of KMO is downstream of cerebral interleukin-1 signaling.•Inhibition of brain KMO reverses depression but not allodynia after nerve injury.