Full-field ERGs obtained using a contact lens electrode with built-in high intensity white light-emitting diodes in beagle dogs can be applied to toxicological assessments

We investigated full-field ERGs in beagle dogs using a contact lens electrode with built-in LED. Experiment 1 was performed to determine the appropriate conditions for stimulus intensity and background illumination. We found that full-field ERGs could be recorded under the following conditions: stimulus intensity: −2.5 log cd*s/m2 in rod responses (RRs), 1.2 log cd*s/m2 in maximal responses (MRs), oscillatory potentials (OPs), cone responses (CRs), 30-Hz flicker responses (FRs), and background illumination: more than 25 cd/m2 in CRs and FRs. Experiment 2 was performed to apply full-field ERGs in beagle dogs to the detection of retinal toxicities. A dog was given one 30 mg/kg dose of sodium iodate (NaIO3) intravenously. ERGs were recorded before administration and 1, 3, 5, 8, 24 h, 7 and 14 days after administration of NaIO3. The RRs disappeared completely at 1 h when MRs and OPs decreased. On the other hand, CRs and FRs were recorded even at 8 h. All responses disappeared at 24 h. These findings indicate that retinal toxicity by NaIO3 is first expressed in rods, followed by cones. These results suggest that full-field ERGs in beagle dogs using an LED contact lens can be used to evaluate toxic effects on rods and cones separately, with the potential to prove more useful than conventional methods for toxicological assessments of developing pharmaceuticals, and can be applied to it.