OBJECTIVE: Traumatic brain injury is a major problem in the disruption of the blood-brain barrier integrity of nerve cells and glial cells. We aimed to investigate the antioxidant effects of losartan, an AT1 receptor blocker, on cell apoptosis with changes in the blood-brain barrier after craniectomy in a rat model. STUDY DESIGN: Male Sprague Dawley rats were randomly divided into 3 groups consisting of 10 rats each. The groups were as follows: control group, trauma group, and trauma+losartan group. After traumatic brain injury, blood samples were taken from the animals and analyzed with various biochemical markers. TUNEL assays and glial fibrillary acidic protein (GFAP) expressions were evaluated immunohistochemically. RESULTS: With TUNEL staining, positive expression was observed in posttraumatic neurons and glial cells. GFAP reaction was positive in degenerative astrocyte processes in the trauma group. In the trauma+losartan group, positive expression in astrocytes with regular structure around the blood vessels was observed. CONCLUSION: Losartan may cause release of cytochrome c via the mitochondrial pathway; however, it also may decrease cellular apoptosis. © 2020 Science Printers and Publishers Inc.. All rights reserved.