Retinal ischemia is a common condition that may lead into vision impairment and blindness. In this study, we evaluated changes separately in On and Off visual responses induced by retinal ischemia. To do this, reversible retinal ischemia was induced in anaesthetized rats by increasing the intraocular pressure until the eye fundus became whitish for either 30 or 60 min. Both electroretinogram (ERG) and multiunit neuronal activity in the superior colliculus (SC) were recorded simultaneously for at least 20 min before, during, and after ischemia. In addition, in normal eyes, intravitreal glycine (Gly) injections were performed to further investigate the mechanisms involved in this process. We found that collicular Off responses were more sensitive to ischemia than On responses. The Off response was the first one to decay at the time ischemia was induced and the last to recover after blood reperfusion. The duration of ischemia also differentially affected both responses. After 30 min of ischemia, 14% of SC recordings failed to recover Off responses. After 1 h of ischemia, the percentage of recordings that failed to recover Off responses increased to 50%. Post-ischemic ERGs remained unaltered in all cases. Intravitreal Gly injections caused suppression of Off responses in the SC. Higher doses caused suppression of both On and Off responses in the SC but with no effect on the ERG at the doses tested. In summary, Off responses were more sensitive than On responses to ischemia suggesting that different mechanisms drive the two types of responses. The recovery of transitory ischemia was not complete in the SC responses whereas the ERG remained unaltered, suggesting that retinal damage produced by ischemia is more prominent in ganglion cells. Our results provide critical information for understanding ischemia repercussions and visual processing in the early visual system.

中文翻译：

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对视网膜缺血的开和关视觉反应的差异敏感性。

视网膜缺血是可能导致视力障碍和失明的常见疾病。在这项研究中，我们分别评估了由视网膜缺血引起的开和关视觉反应的变化。为此，通过增加眼内压直至眼底变白30分钟或60分钟，在麻醉的大鼠中诱发可逆性视网膜缺血。在缺血前，缺血中和缺血后至少20分钟同时记录上丘（SC）中的视网膜电图（ERG）和多单位神经元活动。另外，在正常眼睛中，进行玻璃体内甘氨酸（Gly）注射以进一步研究该过程涉及的机制。我们发现，Coll的Off反应比On响应对缺血更敏感。Off反应是诱导缺血时第一个衰减的反应，最后一次在血液再灌注后恢复。缺血的持续时间也不同地影响了两种反应。缺血30分钟后，14％的SC记录未能恢复Off反应。缺血1小时后，未能恢复Off反应的记录百分比增加到50％。在所有情况下，缺血后ERG均保持不变。玻璃体腔内Gly注射可抑制SC中的Off反应。较高的剂量会导致SC的开和关反应均受到抑制，但在所测试的剂量下对ERG没有影响。总而言之，Off反应比On反应对缺血更敏感，表明不同的机制驱动了两种类型的反应。短暂性脑缺血的恢复在SC反应中并不完全，而ERG仍未改变，这表明由缺血产生的视网膜损伤在神经节细胞中更为突出。我们的结果为了解缺血性反应和早期视觉系统中的视觉处理提供了关键信息。