The slow ERG potentials in hereditary retinal dystrophy of albino and pigmented rats

Abstract

The slow ERG potentials of different sites of generation—PI, PII-related and Slow PIII—were studied at different ages in normal and mutant rats reared in a dark environment. The manifestations of these potentials in the normal rat were similar to the adult rabbit although their amplitudes in comparison to the b-wave were lower. They were peculiarly dependent on age and were highest during the fifth week of age. In the adult, normal pigmented rats, early PI components slightly exceeded Slow PIII but Slow PIII dominated in the records from adult albinos. In the mutant albino or pigmented rats, all slow ERG components were evident at the age of 21 days except the late positive transient of PI. The negative transient of PI disappeared after 26 days but a slow c-wave survived beyond 5 weeks. The iodate-isolated Slow PIII was better preserved than any PI component but it also was sluggish in response to the cessation of illumination. Responses to azide and thiocyanate were well preserved in 4-month-old mutants. The preservation of PI was generally better at any age for the pigmented than the albino mutants. An interpretation of the findings, based upon previous analyses in the rabbit—Slow PIII originating in the distal Müller cell process, PI generated by the pigment epithelium—leads to the conclusions (a) that the electrical properties of the pigment epithelium are not primarily affected in the dystrophic rat and (b) that the accumulation of debris impedes the chemical communication between still functioning photoreceptors and pigment epithelium as well as distal Müller cell processes.