Biomedical subjects

Isamu Nakamura

Publications and source records attributed to Isamu Nakamura.

2 recordsLinked to original sources

PubMed2003

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.

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PubMedDate not supplied

P-VECP can reveal visual toxicity in pigmented rats of repeated doses of ethambutol.

We determined if pattern visually evoked cortical potentials (P-VECPs) in pigmented rats would reveal visual toxicity induced by a drug even when in cases of repeated doses. We obtained appropriate conditions of P-VECPs measurement; the spatial frequency, 0.16 cycle/degree; the mean stimulation luminance, 25 cd/m(2); and the stimulation frequency, 2 Hz. Twelve adult male pigmented rats (Iar: Long-Evans), weighing 210-301 g, were grouped into two (six per group): the control and the ethambutol (EB) 500 mg/kg administered groups. In the EB 500 mg/kg group, the rats were administered EB subcutaneously once daily for 6 weeks. Rats in the control group were given the vehicle subcutaneously once daily for 6 weeks. P-VECPs were carried out prior to initiation of drug administration and at the first, second, third, fourth, and sixth week of the administration. Prolongation of P1 latency in the P-VECPs was evident in the EB 500 mg/kg at fourth and sixth weeks, and there were no marked changes in the control group and no marked changes in P1N1 amplitude in either group. These findings suggest that P-VECPs in pigmented rats can detect chemically induced visual toxicity even in cases of repeated dosing of a drug. This approach is useful for evaluating the visual toxicity of drugs given repeatedly.

Animals↗