The protective effect of limb ischemia postconditioning on ischemic neurons of rat hippocampus by activating MAPK pathway

Objective To elucidate the protective effect of limb ischemia postconditioning on ischemic neurons of rat hippocampus and the possible mechanism related to ERK1/2 phosphorylation and protein expression in hippocampal CA1 region of the rats. Methods Adult male SpragueDawley rats were randomly divided into four groups:sham, ischemia/reperfusion(global cerebral ischemia by four-vessels occlusion,I/R), limb ischaemia postconditioning(Lpost), and Lpost+PD98059 groups. Cresyl violet staining was used to observe survival neurons in hippocampal CA1 region of the rats by light microscope. ERK1/2 phosphorylation and its protein expression were detected by Western blot. Results Western blot analysis showed that the levels of p-ERK1/2 markedly increased after Lpost compared with I/R at the same time point, and the two peaks occurred at 10 min and 1d following reperfusion respectively, but the increase could be suppressed by PD98059. However, there is no significant change for levels of ERK1/2 between I/R and Lpost. Cresyl violet staining showed that I/R clearly reduced the number of survival neurons compared with sham at 1d of reperfusion in the hippocampal CA1 region, the number of survival neurons significantly increased in Lpost group compared with I/R, but decreased in Lpost+PD98059 groups than in Lpost group. Conclusion Limb ischemia postconditioning could protect the cerebral ischemic neurons in hippocampal CA1 of rats, ERK1/2 is activated in this process.