Effects Of M-type(KCNQ) Potassium Channel Openers On Acute Cerebral Ischemia Reperfusion In Rats

Objectives To investigate effects of M-type potassium channel openers of retigabine against brain damage after middle cerebral artery occlusion(MCAO)in rats.Methods 90 SD rats were randomly divided six groups: sham group(n=15),MCAO group(n=15)and RTG-treatment group.RTG-treatment group was also divided into RTG0 h group(n=15),RTG1 h group(n=15),RTG3 h group(n=15)and RTG6 h group(n=15).The temporary middle cerebral artery occlusion reperfusion model was made by the suture method,reperfusion after cerebral ischemia 1h.In RTG-treatment groups,a single dose of 10mg/kg RTG was injected at the designated varying time points(0 hour,1 hour,3 hour and6 hour after the reperfusion).The sham-operated group and MCAO group received the same volume of saline.Infarct size was measured by TTC staining,the neurological function was scored with Longa 5-point scale,HE staining was used to observe the morphological changes of hippocampal neurons.Immunohistochemical staining was used to detect the number of GFAP positive cells,caspase-3 positive cells and Neun positive cells in the ischemic penumbra and in the infarct area.Western blot to detect the number of microglia in penumbra area.The observed value to EXCEL database after finishing using SPSS17.0 statistical software package for data analysis.The analyzed result was expressed as mean±sd((?) ±s).Results 1.Neurological deficit score and cerebral infarction area :In the sham group,no infarction was observed,no neurological deficit.In MCAO group and RTG treatment group,there were different degrees of cerebral infarction lesions in the right middle cerebral artery blood supply area,the left limbs of each group had different degrees of neurological deficits.Compared with MCAO group,the infarct size and Longa score of RTG treatment group were significantly decreased,and the difference was statistically significant(P<0.05).Compared with RTG6 h treatment group,the infarct size and neurological deficit scores of RTG0 h treatment group,RTG1 h treatment group and RTG3 h treatment group were significantly reduced,and the difference was statistically significant(P<0.05).2.HE staining: In the Sham group,the neurons in the hippocampal CA1 region were absent,normal in morphology,and tightly packed.Neuronal edema and necrosis appeared in the hippocampal CA1 region in MCAO and RTG-treated rats,but in the RTG-treated group,the damage of nerve cells in each group was significantly reduced.3.Immunohistochemical staining: In sham group,GFAP positive cells and caspase-3 positive cells are rare in the ischemic penumbra,and the cortical neurons are densely arranged.In the MCAO group and RTG group,the number of GFAP positive cells and caspase-3 positive cells in the penumbra area significantly increased,and the number of Neunpositive cells in the infarct cortex was significantly reduced.Compared with the MCAO group,the number of GFAP positive cells and caspase-3 positive cells in the ischemic penumbra area significantly decreased in the rats treated with RTG,and the number of Neun-positive cells in the infarct cortex increased significantly(P<0.05).Compared with the RTG6 h treatment group,the number of GFAP positive cells and caspase-3 positive cells in the penumbra of the other treatment groups was significantly reduced,and the number of Neun positive cells in the infarct cortex was significantly increased(P<0.05).4.Western blot: There was no CD11 b protein expression in the ischemic penumbra of Sham rats.In MCAO group and RTG group,the expression of CD11 b protein in ischemic penumbra increased significantly.Compared with the MCAO group,the expression of CD11 b protein of the rats treated with RTG was significantly decreased,and the difference was statistically significant(P<0.05).Compared with RTG6 h treatment group,the expression of CD11 b protein of the other treatment groups was significantly reduced,and the difference was statistically significant(P<0.05).Conclusions 1 M-type potassium channel RTG had protective effect to cerebral ischemic reperfusion injury.It can reduce the area of infarction and neurological deficit scores in rats,reduce the proliferation and activation of astrocytes and microglia in the ischemic penumbra,and reduce the apoptosis of neurons in the penumbra of ischemic penumbra.2 When treated after 6 hours of ischemia and reperfusion,M-type potassium channel openers weakened brain protection in rats.