1995 Volume 14 Issue 3-4 Pages 3-4_161-3-4_168
This study was performed to determine the reproducibility of electroretinograms (ERGs) and the effects of anesthesia on the ERG.
Rats were held in the dark for 2 to 3 hours before examination. They were restrained under light ether anesthesia, and topical Benoxyl (0.4% oxybuprocaine hydrochloride) was applied topically to the eyes. A contact lens attached to a recording electrode was placed on the cornea. Ground and reference electrodes were placed on the ear and forehead, respectively. The "a" and "b" waves of ERG were elicited by a single Xenon flash of 0.6 joule at 30 cm from the surface of the eye, and were recorded using a Neuropack Four Mini (MEB-5304, NEC) with a sweep time of 20 msec/div., sensitivity of 200 μV/div., and high and low cuts of 1 kHz and 1 Hz.
The amplitudes and implicit times of "a" and "b" waves obtained from 22 rats were 446±55μV and 18.7±0.9 msec, and 971±116μV and 55.7±4.0 msec, respectively. The coefficient of variation was 12% for amplitude and 5 to 7% for implicit time, suggesting that implicit time was a more consistent parameter than the amplitude. The coefficients of variation of averages of "a" wave amplitudes and implicit times in 5 rats on 3 different days were less than 10%, suggesting acceptable reproducibility.
The effects of pentobarbital 40 mg/kg i.p. on ERG were determined in 5 rats. There were 6% and 20% decreases in amplitude, and 26% and 14% increases in implicit time of "a" and "b" waves, respectively, in pentobarbital-treated rats as compared with pretest values.
In addition, rats were also tested without anesthesia, and nearly steady ERGs could be obtained under one or above one hour dark adaptation.
This method provides relatively consistent amplitudes and implicit times of "a" and "b" waves, and is able to detect the effects of pentobarbital on the electroretinal activity. These data demonstrate that the ERG method is essential to determine electrophysiologically adverse effects of test compounds on the retina.
