How the absence of gravity affects the physiology of human beings is generating global research interest as space exploration, including missions aboard the International Space Station, continues to push boundaries. Here, we examined changes in retinal microcirculation and visual electrophysiology in mice suspended by their tails to simulate the cephalad movement of blood that occurs under microgravity conditions. Tail suspension was performed with a head-down tilt with a recommended angle of 30°. Mice in the control groups were similarly attached to a tether but could maintain a normal position. Morphologically, the 15-day tail-suspended mice showed retinal microvascular dilation, tortuosity, and a relatively long fluorescence retention; however, the average diameter of the major retinal vessels was not notably changed. In addition, optical coherence tomography showed their optic nerve head had an increased diameter. However, the mice could adapt to the change, with microcirculation and the optic nerve head recovering following 30-day tail suspension. Expression of rhodopsin and cone-opsins was not notably changed, and no retinal apoptotic-positive cells were detected between 15- and 30-day tail suspensions. Moreover, the three experimental groups of suspended mice showed normal retinal layers and thickness. Functionally, following 15-day tail suspension, scotopic electroretinograms showed a decline in the oscillatory potentials (OPs), but not in the b wave; simultaneously, the peak time of flash visual evoked potential component N1 was delayed compared to its baseline and the time-matched control. Following 30-day tail suspension, the OPs (O2) amplitude recovered to approximately 97% of its baseline or 86% of the time-matched control level. By simulating cephalad shifting of blood, short-term tail suspension can affect rodent retinal microcirculation, the optic nerve head, and disturb visual electrophysiology. However, the change is reversible with no permanent injury observed in the retina. The mice could adapt to the short-term change of retinal microcirculation, indicating new conditions that could be combined with, or could enhance, simulated microgravity for further studying the impact of short- or long-term outer space conditions on the retina.

中文翻译：

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模拟微重力后，啮齿动物的视网膜微循环和视觉电生理。

引力的缺失如何影响人类的生理学正在引起全球研究兴趣，因为空间探索，包括国际空间站上的飞行任务，继续推动着边界的发展。在这里，我们检查了尾巴悬吊的小鼠视网膜微循环和视觉电生理的变化，以模拟在微重力条件下发生的血液的头部运动。尾部悬吊时，头朝下倾斜，建议角度为30°。对照组中的小鼠类似地附着于系绳，但可以保持正常姿势。从形态上看，15天尾巴悬吊的小鼠表现出视网膜微血管扩张，to曲和相对较长的荧光滞留。然而，主要视网膜血管的平均直径没有明显改变。此外，光学相干断层扫描显示其视神经头直径增大。但是，小鼠可以适应这种变化，尾部悬吊30天后，微循环和视神经头恢复。视紫红质和视锥蛋白的表达没有显着变化，并且在15天和30天的尾巴悬液之间未检测到视网膜凋亡阳性细胞。此外，三个实验组的悬浮小鼠显示正常的视网膜层和厚度。从功能上讲，尾巴悬吊15天后，暗室视网膜电图显示振荡电位（OPs）下降，但b波却没有下降。同时，闪光视觉诱发电位组件N1的峰值时间比其基线和时间匹配的控件要晚。悬吊30天后，OP（O2）振幅恢复到其基线的约97％或时间匹配的对照水平的86％。通过模拟血液的头部移动，短期的尾巴悬吊会影响啮齿动物的视网膜微循环，视神经头并干扰视觉电生理。但是，这种变化是可逆的，在视网膜上没有观察到永久性损伤。小鼠可以适应视网膜微循环的短期变化，表明可以与模拟微重力结合或增强模拟微重力的新条件，以进一步研究短期或长期外太空条件对视网膜的影响。并扰乱视觉电生理。但是，这种变化是可逆的，在视网膜上没有观察到永久性损伤。小鼠可以适应视网膜微循环的短期变化，表明可以与模拟微重力结合或增强模拟微重力的新条件，以进一步研究短期或长期外太空条件对视网膜的影响。并扰乱视觉电生理。但是，这种变化是可逆的，在视网膜上没有观察到永久性损伤。小鼠可以适应视网膜微循环的短期变化，表明可以与模拟微重力结合或增强模拟微重力的新条件，以进一步研究短期或长期外太空条件对视网膜的影响。