Light exposure can reduce selectively or abolish the C-wave of the albino rat electroretinogram

The ERG (electroretinogram) of the albino rat is reported to lack a c-wave. Observations of our own suggested that the conditions of light-rearing are important. Consequently, the authors recorded c-waves in two groups of albino rats. One group was reared from birth in dim illumination (dark-reared) and the other in 12/12 cyclic light (light-reared). Rats were tested after birth from 22 days to about 1 year. All dark-reared animals had a c-wave. Rats reared in cyclic light typically had no detectable c-wave. Physiologic and anatomic evidence suggests this consistent difference, c-waves present in dark-reared animals but absent or diminished in light-reared animals, is probably not due to extensive light induced retinal damage. No consistent differences between the two groups were seen in a- or b-wave thresholds, a- or b-wave intensity-response functions, and in the time-course of b-wave dark adaptation.