Changes in the direct-current electroretinogram of albino rabbits during prolonged intermittent recording.

The study investigated the pattern of the direct-current electroretinogram (ERG) of albino rabbits during prolonged intermittent recording, and whether different initial dark adaptation periods or starting the experiments at different times influenced the results. We examined 27 rabbits under general anesthesia, in three experiments, each comprising nine animals. Five series (experiments 1 and 3) or four series (experiment 2) of ten repeated light stimuli were presented to the eyes with 30 minutes of dark adaptation before experiments 1 and 3, and 90 minutes before experiment 2. The dark adaptation of experiments 1 and 2 began at 10.30 a.m. and that of experiment 3 at 3.30 p.m. The interval between consecutive series of light stimuli was 33 minutes. Stimulus intensity was 680 lux, stimulus duration 10 seconds, and the interval between stimuli 3 minutes. The mean b-wave amplitude of the ten recordings in each series of stimuli increased up to the series beginning 3.5 hours (experiments 1 and 2) or 2.5 hours (experiment 3) after the start of dark adaptation. The mean c-wave amplitude increased throughout experiments 1 and 3, and up to the series beginning 3.5 hours after the start of dark adaptation in experiment 2. The mean a-wave amplitude was more stable. It seemed irrelevant for the long-term development of the mean ERG amplitudes whether the eye was dark adapted (experiment 2) or exposed to repeated light stimuli (experiments 1 and 3) during the first part of the experiment, and whether the experiments started in the morning or in the afternoon.