Abstract
Abstract: :
Purpose:To monitor recovery of rod function in the dark after significant rhodopsin bleaching using the electroretinogram (ERG). Methods:Mice are dark–adapted overnight and anesthetized under dim red light. The pupil of one eye is dilated and a rectal thermometer used to monitor body temperature, which is controlled by a heater on which the mouse lies. The ERG from one eye is recorded with a cotton wick electrode. The head of the mouse is placed in a ganzfeld where both flash and background adapting field are presented as homogeneous full field stimuli. Before light adaptation, the relationship between flash intensity and response amplitude is determined; only one flash, presented once a minute, is used at any intensity. Then the retina is light adapted by 500 or 5000 lux for 3 minutes. The ERG is followed by presenting only one flash every minute, alternating every other minute between maximum and 1/100th maximum intensity. The a– and b–waves for the two intensities are plotted against time in the dark. Results:The percentage recovery of these responses depends on response criterion. With 5000 lux adaptation, b–wave amplitude to maximum flash intensity plateaus for 10–15 minutes before increasing with time while the other responses are undetectable. The b–wave to maximum intensity recovers 60% of its dark adapted value in 40 minutes; the a–wave to minimum intensity recovers only 5% during the same time. The other responses are intermediary. Recovery from 500 lux is quicker but the a–wave to minimum intensity is only 30% recovered at 40 minutes. Conclusions: It takes at least an hour to recover from 500 lux and many hours to recover from a 5000 lux bleach. Sensitivity recovers slower than maximum amplitude. A cone plateau occurs in the b–wave recovery function. The a–wave must reflect rod dark adaptation more than the b–wave.
Keywords: electroretinography: non–clinical • electrophysiology: non–clinical • photoreceptors