Investigation of Visual Function Test in Beagles with Electrophysiological Methods

—Pattern Reversal Electroretinogram (P-ERG)—

Abstract

In order to establish a new method of electrophysiological visual function test in toxicity studies in beagles, we examined the pattern reversal electroretinogram (P-ERG).

P-ERG (transient and steady-state) were recorded on 5 to 11 male beagles (about 10 months of age, body weight 10 to 12kg) sedated by subcutaneous administration of the mixture of xyladine and atropine sulfate, and after complete mydriasis by a drop of mydriatica. The tests were conducted twice at an interval of 1 week through 1 month for assessment of its reproducibility. Both of transient P-ERG and steady-state P-ERG of the beagles were very similar to the corresponding P-ERGs in human respectively. One positive wave was recorded between 36 and 39 msec and another negative wave was recorded between 89 and 105 msec with good reproducibility in the transient P-ERG of the beagles. The amplitude of the transient P-ERG of the beagles was affected by checker size and size of 18 cm gave the highest amplitude. Three peaks (32 through 40, 236 through 242 and 440 through 450 msec) were recorded for 500 msec in the steady-state P-ERG of the beagles.

These findings suggest that the P-ERG can be used in electrophysiological visual function tests in toxicity studies in beagles, because P-ERG were recorded with good reproducibility in beagles, as in human.