NogoA在视觉发育期正常猫和斜视性弱视猫视皮层21a区的表达

背景 视觉发育可塑性的分子机制仍是目前研究的热点,有助于对视觉发育期视功能的异常进行解释和防治,目前轴索生长抑制因子NogoA在视觉发育可塑性中的作用日益受到关注. 目的 观察正常发育猫和斜视性弱视猫视皮层21a区神经元NogoA的表达变化,从分子水平探讨斜视性弱视的发病机制.方法 4周龄幼猫16只按随机数字表法分为正常组和斜视性弱视组,每组8只.斜视性弱视组手术离断右眼外直肌制备成人工内斜视模型,与正常组在同等视觉环境下饲养1周后进行视觉诱发电位(VEP)检测,VEP P100波幅下降及隐含时延长确定为弱视模型制作成功.确定弱视形成后用断颈法处死实验猫,制备猫视皮质区21a区组织切片,采用苏木精-伊红染色检测2个组猫视皮层区的发育情况,应用免疫组织化学法观察正常组和斜视性弱视组视皮层21a区NogoA的表达并进行定量比较. 结果 斜视性弱视组猫P-VEP P100隐含时为(108.50±6.95)ms,右眼/左眼P100振幅比值为0.35±0.09,正常组为(98.10±7.07)ms,右眼/左眼P100振幅比值为0.83±0.14,差异均有统计学意义(t=4.450,P=0.005；t=5.970,P=0.005).2个组视皮质21a区苏木精-伊红染色表明斜视性弱视组视皮质神经元的数目无明显减少,但神经元细胞质突起变短或消失.免疫组织化学染色表明,NogoA阳性细胞均存在于Ⅱ～Ⅵ层,呈棕黄色表达,位于神经元一侧.正常组视皮质21a区Ⅱ～Ⅵ层可见NogoA阳性染色细胞,斜视性弱视组Ⅱ/Ⅲ、Ⅳ、V/Ⅵ区NogoA表达的免疫阳性细胞密度分别为(387.37±2.01)、(354.58±1.85)、(289.68±1.81)个/mm2,明显高于正常组的(161.39±1.98)、(128.93±1.26)、(96.25±1.49)个/mm2,差异均有统计学意义(t=-160.400、-201.890、-164.740,P=0.000). 结论 NogoA在调控视觉发育敏感期及其可塑性中可发挥关键性作用.

Expression of NogoA in 21a area of visual cortex in visual developing normal cat and strabismic amblyopia cat

Background The study of the molecular mechanism of visual plasticity is helpful for the explaining and prevention of strabismus and amblyopia. The effect and significance of NogoA in the strabismus and amblyopia formation are attracting more attention. Objective The present study was to investigate the expression of NogoA in 21a area of visual cortex in strabismic-induced amblyopia cats and explore the possible molecular mechanism of strabismic-induced amblyopia. Methods Sixteen 4-week old clean cats were randomizedly divided into normal group and strabismic-induced amblyopia group and eight for each group. The strabismic-induced amblyopia models were created by cutting off the external rectus in 8 cats. Pattern visual evoked potentials （P-VEP） were recorded 1 week after operation and compared with normal cats, and depression of amplitude and prolongation of implied time of Pl00 wave were as the successful criterion of model. The 200 ml paraformaldehyde was infused via heart to fax the brain under the deep anesthesia and then the eats were sacrificed and the brain cortex sections were prepared. The morphology of 21a zone of cat visual cortex was examined by haematoxylin and eosin staining,and the expressions of NogoA in 21a area of visual cortex were detected by immunohistochemistry with a monoclonal anti-NogoA antibody. The use of the animals complied with the Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.