Jehle Thomas, Wingert Karin, Dimitriu Cornelia, Meschede Wolfram, Lasseck Julia, Bach Michael, Lagrèze Wolf A
University Eye Hospital Freiburg, Freiburg, Germany.
Invest Ophthalmol Vis Sci. 2008 Mar;49(3):1056-64. doi: 10.1167/iovs.07-1050.
To identify objective criteria to quantify visual function in the rat for developing therapeutic strategies to protect neuronal cells after ischemia. The impact of ocular ischemia on luminance and frequency-modulated contrast vision was compared with the function of outer retinal cells and the number of intact retinal ganglion cells (RGCs).
Ischemia was induced in Brown-Norway rats by elevating the intraocular pressure to 120 mm Hg for 30, 45, 60, and 90 minutes. Visual function was evaluated by visual evoked potentials (VEPs) in awake, freely moving rats. Retinal function was analyzed with scotopic and photopic electroretinography (ERG). RGCs were quantified in retinal flatmounts after postischemic injection of tracer into the superior colliculus.
The response to flicker stimulation in VEP recordings decreased as the ischemic episodes increased. The susceptibility to ischemic damage was more pronounced when potentials were evoked with stimuli at higher frequencies. In ERG recordings, ischemia reduced oscillatory potentials and photopic flicker responses more intensely than scotopic a- and b-waves. In counting the RGCs, the reduced cell density correlated significantly with all electrophysiological parameters. The duration of ischemia with half-maximal inhibitory effect was between 36 and 58 minutes for VEPs and between 36 and 41 minutes for ERG, and it was 51 minutes for RGCs.
The amounts of reduction in VEPs, ERG, and RGCs differed as the duration of ischemia increased. The electrophysiological parameters presented in this study may serve as a useful addition to morphologic evaluations in future neuroprotection studies in vivo.
确定量化大鼠视觉功能的客观标准，以制定缺血后保护神经元细胞的治疗策略。将眼缺血对亮度和调频对比度视觉的影响与视网膜外层细胞功能及完整视网膜神经节细胞（RGCs）数量进行比较。
通过将棕色挪威大鼠眼压升高至120 mmHg持续30、45、60和90分钟诱导缺血。在清醒、自由活动的大鼠中通过视觉诱发电位（VEP）评估视觉功能。用暗视和明视视网膜电图（ERG）分析视网膜功能。在缺血后向上丘注射示踪剂后，在视网膜平铺标本中对RGCs进行定量。
随着缺血发作次数增加，VEP记录中对闪烁刺激的反应降低。当用更高频率的刺激诱发电位时，对缺血损伤的易感性更明显。在ERG记录中，缺血对振荡电位和明视闪烁反应的降低作用比对暗视a波和b波更强烈。在计数RGCs时，细胞密度降低与所有电生理参数显著相关。对VEP产生半数最大抑制作用的缺血持续时间在36至58分钟之间，对ERG为36至41分钟，对RGCs为51分钟。
随着缺血持续时间增加，VEP、ERG和RGCs的减少量不同。本研究中呈现的电生理参数可能有助于在未来体内神经保护研究中对形态学评估进行补充。
