BCL-2 IS EXPRESSED IN NEURONS THAT SURVIVE FOCAL ISCHEMIA IN THE RAT

EXPRESSION of the proto-oncogene bcl-2 prevents programmed cell death in vitro, but it is not known whether bcl-2 plays a role in determining cell survival after cerebral ischemia. Using immunohistochemistry and Western blot analysis, bcl-2 protein expression was studied in the rat brain 24 h following 60 or 120 min of temporary focal ischemia. Sixty minutes of ischemia induced bcl-2 protein in neurons throughout the frontoparietal cortex in noninfarcted regions, whereas 120 min of ischemia induced bcl-2 in neurons only just outside the margin of the infarction. bcl-2 protein was also induced in glial cells, mainly microglia, border zone of the infarction. In the infarcted regions of caudate and cortex, bcl-2 protein was exclusively induced in endothelial cells and the vessel walls. Western blot revealed a characteristic single band at 26 kDa only in ischemic samples. These data show that bcl-2 is induced in sublethally injured cells and suggest that bcl-2 could play a role in determining cell survival in cerebral ischemia.