不同给药途径的聚乙二醇对大鼠视神经切断后视网膜神经节细胞存活的影响

目的:比较不同给药途径的聚乙二醇(PEG)对成年大鼠视神经切断后视网膜神经节细胞(节细胞)存活的影响。方法:72只成年SD大鼠左眼球后1.5 mm处横断视神经,眶侧断端留置浸有荧光金的明胶海绵以逆行标记存活的节细胞。术后立即尾静脉注射1 ml 30%PEG(尾静脉注射PEG组)或等体积生理盐水(尾静脉注射盐水对照组),或在视神经眶侧断端留置浸有50%PEG(局部PEG组)或生理盐水(局部盐水对照组)的明胶海绵。四组动物(n=18)分别存活2、7 d或14 d(每时间点,n=6)后处死,取术侧视网膜,平铺计数存活节细胞并计算出节细胞密度。结果:术后7 d尾静脉注射PEG组存活节细胞平均密度(1121.43 mm2±42.69/mm2)显著高于尾静脉注射盐水对照组(846.67/mm2±58.19/mm2,P<0.05),而2 d和14 d时间点两组节细胞密度间无显著性差异(P>0.05);局部PEG组节细胞密度在各时间点与局部盐水对照组相比均无显著性差异(P>0.05);在7 d点,尾静脉注射PEG组节细胞密度显著高于局部PEG组(774.43/mm2±50.49/mm2,P<0.05)。结论:PEG能在视神经切断后一定时间内延缓节细胞死亡,且这种神经保护作用有赖于PEG的给药途径。

Effects of polyethylene glycol on axotomized retinal ganglion cells after rat optic nerve transection

Objective: To compare the effects of polyethylene glycol(PEG) administered through different approaches on the survival of retinal ganglion cells(RGCs) after optic nerve(ON) transection in adult rats.Methods: Seventy-two adult Sprague-Dawley rats received left ON transection 1.5 mm behind the eyeball,followed by the placement of a small piece of Gelform soaked in FluoroGold onto the ocular ON stump to retrogradely label the surviving RGCs.Immediately after ON transection,these animals received intravenous injection of 1 ml 30%(M/W) PEG(IV PEG group) or the same volume of sterile saline(IV saline control group) through tail vein,or the local placement of a small piece of Gelform soaked in 50%(M/W) PEG(local PEG group) or saline(local saline control group) onto the ON stump.The animals(n=18 for each group) were allowed to survive for 2,7 or 14 days(n=6 for each time point),respectively,before the left eyes were enucleated to count the number and calculate the density of surviving RGCs in each retina.Results: The mean RGC density in IV PEG group(1121.43±42.69/mm2) was significantly higher than that in IV saline control group(846.67±58.19/mm2,P<0.05) at 7 day time point,but no difference in the RGC densities were detected between these 2 groups at 2 and 14 day points(P>0.05).The RGC densities in local PEG group were similar to those in local saline control group at all 3 time points(P>0.05).A significant higher RGC density was found in IV PEG group in comparison with local PEG group(774.43±50.49/mm2,P<0.05) at 7 day point.Conclusion: PEG can delay the death of axotomized RGCs for a certain period after rat ON transection and this neuroprotective effect of PEG rely on the administering approach of the chemical.