Cortical neurogenesis in adult rats after reversible photothrombotic stroke

Neurogenesis occurs throughout life in the dentate gyrus of hippocampus and subventricular zone, but this phenomenon has rarely been observed in other brain regions of adult mammals. The aim of the current study was to invest igate the cell proliferation process in the ischemically challenged region- at-risk; after focal cerebral ischemia in the adult rat brain. a reversible photothrombotic ring stroke model was used, which features sustained hypop erfusion followed by late spontaneous reperfusion and a remarkable morpholo gic tissue recovery in the anatomically well defined somatosensory cortical region-at-risk. Twelve-week-old male Wistar rats received repeated intrape ritoneal injections of the cell proliferation specific marker 5-bromodeoxyu ridine (BrdU) after stroke induction. Immunocytochemistry of coronal brain sections revealed that the majority of BrdU-positive cells were of glial, m acrophage, and endothelial origin, whereas 3% to 6% of the BrdU-positive ce lls were double-labeled by BrdU and the neuron-specific marker Map-2 at 7 a nd 100 days after stroke onset in the region-at-risk. They were distributed randomly in cortical layers II-VI. Three-dimensional confocal analyses of BrdU and the neuronal-specific marker Neu N by double immunofluorescence co nfirmed their colocalization within the same cells at 72 hours and 30 days after stroke induction. This study suggests that, as a potential pathway fo r brain repair, new neurons can be generated in the cerebral cortex of adul t rats after sublethal focal cerebral ischemia.