Role of c-fos in protective effect of limb ischemic preconditioning against injuries induced by cerebral ischemia/reperfusion in rats

Objective To investigate the role of c-fos in the protective effect of limb ischemic preconditioning(LIP) against cerebral ischemia-reperfusion injuries.Methods Fifty-four Wistar rats with vertebral arteries permanently occluded were divided into sham operation group,cerebral ischemic group and LIP+cerebral ischemic group.Cerebral ischemic group and LIP+cerebral ischemic group were further divided into 1,6,24 and 72 h groups according to the time of reperfusion after cerebral ischemia respectively.Changes in the expression of c-fos in the hippocampus were observed using immunohistochemical method.Results There was no obvious c-fos positive expression in every subfield of hippocampus in sham operation group.In cerebral ischemic group,c-fos expression was found in the CA3 subfield and dentate gyrus rather than the CA1 subfield,especially at 6 h after cerebral ischemia,and this expression began to be diminished at 24 h and disappeared at 72 h after cerebral ischemia.In LIP+cerebral ischemic group,some weak immunoparticles were found in the hippocampus CA1 at 1 h after cerebral ischemia.The expression of c-fos was obviously enhanced at 6 h,the number and total area of positive cells and optical density were significantly higher compared with sham operation and cerebral ischemia 6 h groups(P(0.01).) The expression of c-fos tended to decrease at 24 h,and recovered to level of sham operation group level at 72 h.Conclusion The protection conferred by LIP against cerebral ischemia/reperfusion injuries may be associated with the increased expression of c-fos in the hippocampus CA1 induced by LIP.