Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
Department of Neurobiology, Northwestern University, Evanston, IL, USA.
Curr Eye Res. 2024 Jan;49(1):53-61. doi: 10.1080/02713683.2023.2264544. Epub 2024 Jan 3.
To understand the mechanism of changes in the c-wave of the electroretinogram (ERG) in diabetic rats, and to explore how glucose manipulations affect the c-wave.
Vitreal ERGs were recorded in control and diabetic Long-Evans rats, 3-60 weeks after IP vehicle or streptozotocin. A few experiments were performed on Brown Norway rats. Voltage responses to current pulses were used to measure the transepithelial resistance of the retinal pigment epithelium (RPE).
During development of diabetes the b-wave amplitude progressively decreased to about half of the initial amplitude after a year. In contrast, the c-wave was strongly affected from the very beginning (3 weeks) of diabetes. In control rats, the c-wave was cornea-positive at lower illuminations but was cornea-negative at higher (photopic) illumination. In diabetics, the whole amplitude-intensity curve was shifted toward negativity. The magnitude of this shift was markedly affected by acute glucose manipulations in diabetics but not in controls. Increased blood glucose made the c-wave more negative, and decreased blood glucose with insulin had the opposite effect. Experimentally induced acidification of the retina had a small effect that was different from diabetes, shifting the c-wave toward positivity, slightly in controls and more noticeably in diabetics. One reason for the significant negativity of the diabetic ERG was a decrease of the cornea-positive response of the RPE due to a decrease of the transepithelial resistance.
The ERG c-wave is more negative in diabetics than in control animals, and is far more sensitive to changes in blood glucose. The increased negativity is largely if not entirely due to changes in the transepithelial resistance of the RPE, an electrical analog of the breakdown of the blood-retinal barrier observed in other studies. The sensitivity of the c-wave to glucose in diabetics may also be due to changes in transepithelial resistance.
了解糖尿病大鼠视网膜电图（ERG）c 波变化的机制，并探讨葡萄糖处理如何影响 c 波。
在玻璃体 ERG 记录中，使用 IP 载体或链脲佐菌素分别处理对照和糖尿病 Long-Evans 大鼠 3-60 周。在一些实验中，还使用了 Brown Norway 大鼠。使用电流脉冲电压反应来测量视网膜色素上皮（RPE）的跨上皮电阻。
在糖尿病发展过程中，b 波振幅逐渐下降，一年后约为初始振幅的一半。相比之下，c 波从糖尿病开始（3 周）就受到强烈影响。在对照大鼠中，c 波在较低照度下为角膜正性，但在较高（明视）照度下为角膜负性。在糖尿病大鼠中，整个振幅-强度曲线向负值方向移动。这种移位的幅度受糖尿病大鼠急性葡萄糖处理的显著影响，但不受对照大鼠的影响。升高血糖使 c 波更负，胰岛素降低血糖则产生相反的效果。实验诱导的视网膜酸化作用较小，与糖尿病不同，使 c 波向正性移动，在对照大鼠中略有变化，在糖尿病大鼠中更明显。糖尿病 ERG 明显负性的一个原因是由于跨上皮电阻降低，RPE 的角膜正性反应降低。
糖尿病大鼠的 ERG c 波比对照动物更负，对血糖变化更敏感。增加的负性主要（如果不是全部）归因于 RPE 跨上皮电阻的变化，这是其他研究中观察到的血视网膜屏障破裂的电模拟。糖尿病患者 c 波对葡萄糖的敏感性也可能与跨上皮电阻的变化有关。
