左旋多巴甲酯对剥夺性弱视猫视皮层17区神经细胞的影响

Effects of L-dopa methyl ester on visual cortex area 17 neuron in monocular deprivation cat

目的观察不同剂量的左旋多巴甲酯对剥夺性弱视猫模型视皮层17区神经细胞凋亡情况以及神经生长因子(NGF)和FOS蛋白表达的影响,探讨左旋多巴甲酯对弱视的治疗效果及其作用机制。方法健康的幼猫30只随机分成6组:左旋多巴甲酯高(LDMEH)、中(LDMEM)、低(LD-MEL)剂量组、阳性对照组(PC)、模型对照组(MC)及正常对照组(NC),每组5只。除了正常组,于4周龄时参照Hubel经典实验方法对各组幼猫进行麻醉后的左眼单纯上下睑缝合建立剥夺性弱视,12周后打开缝合眼并开始给药,每天灌胃左旋多巴甲酯20,40,80 mg.kg-1,阳性对照组为左旋多巴40 mg.kg-1,正常组与模型组为等剂量生理盐水,每天1次持续30 d。进行Nissl染色观察,TUNEL检测法观察视皮层神经细胞的凋亡情况,经免疫组化技术检测视皮层17区神经细胞中NGF以及FOS蛋白的表达情况。结果左旋多巴甲酯有效地降低了弱视眼视皮层17区中的神经细胞凋亡率。模型对照组弱视眼视皮层17区NGF和FOS免疫阳性细胞数量明显低于正常对照组,差异有统计学意义(P<0.01)。给药治疗后各组视皮层17区NGF和FOS免疫阳性细胞密度较模型对照组均为增加,差异有统计学意义(P<0.01或P<0.05)。结论左旋多巴甲酯对视皮层17区中神经细胞有保护作用,通过上调内源性NGF和FOS蛋白的表达来修复剥夺性弱视造成的结构与功能缺陷,可能与它们共同协调作用下重塑中枢视觉通路有关。

Aim To observe the effects of different does of the Levodopa（L-dopa） methyl ester（LDME） on the expression of TUNEL positive cells,NGF and FOS protein in neurons of the visual cortex of cats with monocular deprivation（MD）,and explore the therapeutic effect of LDME on amblyopia and its mechanism.Methods 30 normal cats were randomly divided into 6 groups（5 cats in each group）： low dose（LDMEL）,medium dose（LDMEM）,and high dose of L-dopa methyl ester（LDMEH）,positive control group（PC）,normal control group（NC） and model control group（MC）.Referring to the classic experiments of Hubel,the kittens in each group were anesthetized and visually deprived by suturing the lids of the left eyes to perform the monocular deprivation amblyopia,then eye closure was open and treated with drug after 12 weeks（the normal control group was excluded）.L-dopa methyl ester（20,40,80 mg·kg-1）,L-dopa（40 mg·kg-1） and normal saline were given respectively to the corresponding animals for 30 days.The Nissl staining and apoptosis level with TUNEL staining were recorded to check the cats＇ visual cortex features.The immunohistochemistry technique was used to detect the expression of NGF and FOS protein.Results L-dopa methyl ester effectively reduced the apoptosis index of the nerve cells in visual cortex area 17 of amblyopic eye.The number of NGF and FOS immunoreactive cells in amblyopic eye of visual cortex area 17 in model control group was significantly lower than the normal control group,the difference was statistically significant（P0.01）.After treatment of drug,the density of NGF and FOS immunoreactive cells in amblyopic eye of visual cortex area 17 in each group increased compared with the model control,the difference was statistically significant（P0.01 or P0.05）.Conclusion L-dopa methyl ester may prevent amblyopia-induced apoptosis and make a restoration of structure and visual functional defect in amblyopic cat by enhancing the NGF and FOS protein expression in the visual cortex during the visual development,which could rebuild the visual pathway in monocular amblyopia by the role of coordination.