The adipocytokine,apelin-13,is an abundantly expressed peptide in the nervous system.Apelin-13 protects the brain against ischemia/reperfusion injury and attenuates traumatic brain injury by suppressing autophagy.However,secondary apelin-13 effects on traumatic brain injury-induced neural cell death and blood-brain barrier integrity are still not clear.Here,we found that apelin-13 significantly decreases cerebral water content,mitigates blood-brain barrier destruction,reduces aquaporin-4 expression,diminishes caspase-3 and Bax expression in the cerebral cortex and hippocampus,and reduces apoptosis.These results show that apelin-13 attenuates secondary injury after traumatic brain injury and exerts a neuroprotective effect.