左旋多巴对形觉剥夺性弱视猫视皮层17区神经生长因子的影响

Effects of levodopa on nerve growth factor in visual cortex of kitten

目的观察左旋多巴对猫形觉剥夺性弱视的治疗作用及其对视皮层17区神经生长因子(NGF)表达的影响。方法18只4周龄幼猫分为正常组、单眼剥夺组、左旋多巴组,每组6只。通过单眼眼睑缝合制备形觉剥夺弱视模型,观察不同干预条件下各组视觉诱发电位(P-VEP)的P1隐含值及波幅,应用免疫组织化学法测定各组视皮层17区NGF的差异。结果单眼剥夺组剥夺眼P100波隐含值延长,波幅降低,与正常组及对侧眼比较,差异均有统计学意义(P<0.01),左旋多巴组双眼P-VEP各指标与正常组比较,差异均无统计学意义(P>0.05)。剥夺组视皮层NGF免疫阳性细胞密度为80.23±9.54,正常组为111.83±7.49,2组比较差异有统计学意义(P<0.01);左旋多巴组为118.06±12.37,与正常组比较差异无统计学意义(P=0.94)。结论敏感期内剥夺性弱视幼猫视皮层17区NGF的表达减弱。左旋多巴干预治疗后,NGF表达明显增加,弱视眼P-VEP明显改善,左旋多巴能促进实验猫弱视眼的视功能改善。

Objective Nerve growth factor （NGF） is thought to be one of regulating factors of cellular function during the visual plasticity period. Levodopa is a neurotransmitter in central nerve system. Its mechanism of improving the visual function in amblyopia is unclear. Present study was to observe the role of levodopa in treating monocular deprived amblyopia and explore the effects of levodopa on the expression of NGF in visual cortex. Methods The animal models of monocular form deprived anablyopia were established in the right eyes of 12 4-week-old domestic cats by suturing the eyelid for 2 weeks and then the left eyes were reverse sutured. The 6 cats from mmtels received 20 mg/kg of levodopa by oral administration. Other 6 normal cats were as normal controls. Pattern VEP （P-VEP） was recorded to check the visual acuity of the cats. The cell number density of NGF expression in visual cortex area 17 was detected and calculated by immnnochemistry and expressed as positive number/field. Results The amplitude of P,t0 of P-VEP was significantly declined in monocular deprived eyes compared with fellow eyes and normal eyes in 2 weeks after monocular deprivation （P 〈 0.01 ）. However, after administration of levodopa,the amplitude of Pl00 recovered to normal 2 weeks later,presenting a insignificant difference between levodopa treating group and normal group （P 〉 0.05 ）. The latency of P100 was followed the same pattern between two groups. The NGF positive ceils were decreased in monocular deprived group compared with normal group and levodopa group （ 80. 23± 9.54 vs 111.83 ±7.49,80. 23 ±9. 54 vs 118.06 ± 12.37,P 〈0. 01 ）, but no significant difference in NGF positive cells was found between normal group and levodopa group （111.83 ±7.49 vs 118.06 ± 12.37, P = O. 94）. Conclusion Levodopa is supposed to accelerate the recovery of visual function in amblyopic eat by enhancing the NGF expression in visual cortex area 17 during the critical period of visual development.