Electroretinogram Analysis in Diabetic Mice

ERGs were performed 4 months after the induction of diabetes (6 months of age). After overnight dark adaptation, mice were anesthetized with ketamine (87.5 mg/kg) and xylazine (12.5 mg/kg), the cornea was anesthetized with 0.5% proparacaine hydrochloride (Medline, 17478-0263-12), and the pupils were dilated with 2.5% phenylephrine hydrochloride (Medline, 17478-0201-15). Briefly, mice were placed on the temperature-regulated heated ERG instrument (Diagnosys, Lowell, MA), and the retinal responses recorded by placing electrode on each cornea; the subdermal reference was placed on the nose, and ground needle electrodes were placed at the base of the tail^{56 (link)}. The full-field flash ERG responses from both eyes were recorded on mice dark-adapted overnight followed by light-adaptation (10 min of 30 cd/m2 light); the flash intensities were 0.01, 0.1, 0, 1, and 10 cd*s/m² with a 2- to 5-s interstimulus interval. The amplitude of ERG a-wave was measured from the trough of the first corneal negative deflection to the pre-stimulus baseline. The amplitude of the b-wave was calculated from the a-wave amplitude to the peak of the b-wave. The c-wave was measured in response to 2.5 cd*s/m² stimuli immediately before light adaptation. All ERG a-, b-, and c-wave amplitudes were automatically calculated by Espion V6 software (Diagnosys LLC).