神经生长因子对单眼剥夺大鼠视觉中枢nNOS表达的影响

Nerve growth factor on expression of neuronal nitric oxide synthase in optic center of monocular deprived rats

目的观察单眼剥夺（monocular deprivation，MD）大鼠神经生长因子（nerve growth factor，NGF）治疗前后视中枢神经型一氧化氮合酶（neuronal nitric oxide synthase，nNOS）阳性神经元表达的改变。方法健康雄性SD大鼠，随机分为正常组（N组）、MD组、MD脑室内注射NGF组（MD＋NGF组）和MD脑室内注射生理盐水组（MD＋NS组）。剥夺自14d龄开始，每组随机分为2个亚组，分别于28d、42d龄处死，MD＋NGF组和MD＋NS组中的2个亚组分别于14d、28d龄开始行脑室内注射B—NGF或NS。采用免疫组织化学染色法观察视中枢nNOS阳性神经元的表达。结果nNOS阳性神经元在视皮层V1区Ⅱ～Ⅵ层和外侧膝状体背核散在分布。28d龄时，MD组Vl区nNOS阳性神经元数密度（除Ⅳ层外）、胞体截面积和树突总长度分别为（1．47±1．14）mm^-2、（201．84±37．00）μm2、（423．86±105．86）μm，较N组明显减少，差异有统计学意义（P〈0．05）；MD＋NGF组上述表达较MD组及MD±NS组明显增强，差异有统计学意义（P〈0．05），与N组比较差异无统计学意义（P〉0．05）。42d龄时，MD组V1区胞体截面积减小、外侧膝状体背核nNOS阳性神经元数密度降低，与N组比较差异有统计学意义（P〈0．05）；MD＋NGF组上述表达与MD组及MD4-NS组比较，差异无统计学意义（P〉0．05）。结论视觉发育具有可塑性，NO是影响视觉发育的一个环节。在视觉发育敏感期内，外源性提供NGF，可以促进视觉中枢nNOS增多，从而拮抗剥夺效应。

Objective To investigate the changes of positive neurons expression of neuronal nitric oxide synthase （nNOS） before and after treated with nerve growth factor （NGF） in rats with monocular deprivation （MD）. Methods Healthy male SD rats were randomly divided into four groups ： normal group （ N group ）, MD group, MD and intraventricular injection of NGF group （MD with NGF group）, and MD with intraventricular injection of normal sodium group （ MD with NS group ）. The rats were deprived on postnatal 14 days. Each group was divided into two subsets, rats of which were killed on postnatal 28 days and 42 days, respectively. Intraventricular injection of β-NGF or NS was performed in two subsets of MD with NGF group or of MD with NS group on postnatal 14 days and 28 days, respectively. Positive neurons expression of nNOS was observed with immunohistochemical staining. Results The positive neurons of nNOS scattered in all layers from Ⅱ to Ⅵ of V1 region and in dorsal lateral geniculate nucleus. On postnatal 28 days, there were significant decreases about the density of numbers of positive neurons of nNOS （ except layer Ⅳ） （ 1.47 ＋ 1.14 ） mm -2, cell secar（201.84 ＋ 37.00） μm2 and dendritic length（423.86 ＋ 105.86） μm in V1 region of MD group compared with those of N group （ all P 〈 0.05 ）, those of MD with NGF group were significantly higher than those of MD group or of MD with NS group （ all P 〈0. 05 ）, but no significant difference was found between those of MD with NGF group and those of N group（ all P 〉0.05 ）. On postnatal 42 days,there were significant decreases about the cell secar in V1 region and the density of numbers in dorsal lateral geniculate nucleus of MD group compared with those of N group （ both P 〈 0.05 ）, but there was no statistical difference about those of MD with NGF group compared with MD group or MD with NS group（all P 〉 0. 05 ）. Conclusions The visual development is fictile, and NO plays a role. In sensitive period of visual development, the ectogenic NGF is effective in preventing the effects of MD in rat through increasing nNOS at optic centre.