Cortical neurogenesis in adult rats after transient middle cerebral artery occlusion

Background and Purpose-This study explored the possible occurrence of newly generated nerve cells in the ischemic cortex of adult rats after middle cerebral artery occlusion and reperfusion. Methods-Nine- to 10-week-old male Wistar rats were subjected to 2 hours of middle cerebral artery occlusion by the monofilament method. Rats received repeated intraperitoneal injections of the cell proliferation-specific marker 5-bromodeoxyuridine (BrdU) after stroke induction. Brain sections were processed for immunohistochemistry with an avidin-biotin complex-alkaline phosphatase and/or -peroxidase method. Brain sections processed with double-immunofluorescent staining were further scanned by confocal microscopy. Results-Interspersed among the predominantly newly formed glial cells, some cells were double labeled by BrdU and 1 of the neuron-specific markers, Map-2, beta -tubulin III, and Neu N, at 30 and 60 days after stroke onset. These cells were randomly distributed throughout cortical layers II through VI, occurring with highest density in the ischemic boundary zone. Three-dimensional confocal analyses of BrdU and the neuron-specific marker Neu N confirmed their colocalization within the same cortical cells. Conclusions-This study suggests that new neurons can be generated in the cerebral cortex of adult rats after transient focal cerebral ischemia. Cortical neurogenesis may be a potential pathway for brain repair after stroke.