Isamu Nakamura

Visually evoked cortical potentials obtained using checker patterns can detect ethambutol-induced visual toxicity in albino rats

We determined whether visually evoked cortical potentials obtained using checker patterns (P-VECPs) and albino rats would reveal visual damage induced by ethambutol (EB). Findings were compared in cases of detection of visual damage between by P-VECPs and by flash visually evoked cortical potentials (F-VECPs). Twelve adult albino male Crj:CD(SD)IGS rats were grouped into four, three per group: control, 250PS, 500PS, and 500SC groups. In the 250PS and 500PS groups, rats were administered EB orally for the first 2 weeks and then subcutaneously for the second 2 weeks to 250 and 500 mg/kg, respectively. In the 500SC group, rats were given 500 mg/kg of EB subcutaneously for 4 weeks. Rats in the control group were given the vehicle orally for the first 2 weeks and then subcutaneouly for the second 2 weeks. P-VECPs and F-VECPs were carried out prior to initiation of drug administration and at the 1st, 2nd, 3rd, and 4th weeks of the administration. Prolongation of P1 latency in the P-VECPs was evident in both the 500PS and the 500SC groups at the 4th week, while no marked changes were observed in the F-VECPs. Thus, P-VECPs in albino rats can detect visual damage induced by EB even when F-VECPs cannot do so. These studies suggest that P-VECPs are useful for evaluating the visual toxicity of drugs.