Evaluation of different recording parameters to establish a standard for flash electroretinography in rodents

Different electrodes and stimulus protocols commonly used for electroretino graphy in rodent eyes were compared for convenience of use, degree of damag e to corneal epithelium, and for magnitude of amplitude, reproducibility, l eft versus right eye accuracy, and reliability of recorded parameters of th e flash electroretinogram (ERG). Adult C57BL/6 pigmented mice and albino Wi star rats were used to determine scotopic ERGs in response to Ganzfeld or s trobe-light stimulation and light-adapted (photopic) ERGs recorded from bot h eyes at the same time. Test-retest data were used for statistical analyse s to compare a monopolar gold-wire contact lens electrode (CLE), a cotton-w ick silver-silver chloride electrode (CSCE), a DTL fiber electrode (DTLE), and a circular stainless steel wire electrode (SSE). Corneas were evaluated for abrasion after ERG recordings using fluorescein staining and also for the time taken, ease of insertion, and re-insertions required for the diffe rent electrodes. Compared to CSCE, DTLE, and SSE, the ERG potentials record ed by CLE had significantly larger scotopic amplitudes and oscillatory pote ntials under strobe or Ganzfeld stimulation and for light-adapted ERG b-wav e amplitudes in both mice and rats. In analyzing test-retest data of scotop ic ERG a-wave and b-wave amplitudes, the intraclass correlation coefficient showed the best agreement for the CLE (range 0.61-0.94) compared to the SS E (0.13-0.77), DTLE (0.02-0.69), and CSCE (0.12-0.51). In mice and rats, lo gistic regression analyses revealed significant correlations for amplitudes of most scotopic ERG parameters between contralateral eyes obtained with C LE and for some ERG components recorded by SSE. When comparing ERG amplitud es for stimulation by strobe or Ganzfeld, the difference was least with the CLE compared to DTLE, CSCE, or SSE. The time taken to insert the four diff erent electrodes was greatest for the CLE in both mice and rats. The extent of corneal abrasion resulting from electrode use in mice was largest for t he SSE followed by the CLE. However, in rats there was almost no corneal da mage after ERG recordings with the CLE. Because of the stability of eye con tact, the CLE allows ERGs to be determined over a longer recording session. Recording of scotopic and photopic (light-adapted) ERGs in rodents with mo nopolar gold-wire contact lens electrodes provides greater amplitudes and h igher reproducibility when compared to other commonly used corneal electrod es. These electrodes are significantly better overall than others that were evaluated and should be considered for a standard protocol to monitor reti nal function in rodent eyes. (C) 2001 Published by Elsevier Science Ltd.