Full-field electroretinography obtained using a contact lens electrode with built-in high-intensity white-light-emitting diodes can be utilized in toxicological assessments in rats.
Full-field electroretinography (ERG) using contact lenses with built-in LED was performed on albino rats, and used to evaluate the visual toxicity of sodium iodate (NaIO(3)). Experiment 1 was carried out to determine the optimal conditions in rats relating to stimulus intensity, background illumination, and light adaptation period. As a result, we found that a full-field ERG was recorded under the following conditions: stimulus intensity: -3.5 log cd s/m(2) in rod response; background intensity and light adaptation period: 10 cd/m(2) and 10 min in cone and flicker responses. Experiment 2 was carried out to confirm the usefulness of full-field ERG using rats with retinal toxicities induced by NaIO(3). Male rats were given NaIO(3) intravenously at a dose of 50 mg/kg. ERG was recorded before administration and after 3, 8, 24 h, and 7 days of administration, and histopathological analysis was conducted after 8 h of administration. The rod response disappeared completely at 3 h, based on a reduced maximal response and oscillatory potentials. On the other hand, cone and flicker responses were still present at 8 h. All responses disappeared on the 7th day. These findings indicate that the retinal toxicity induced by NaIO(3) was expressed first in rods, followed by cones. There were no microscopical changes after 8 h of administration, although the rod responses had completely disappeared by this time. These results suggest that full-field ERG in rats using an LED contact lens is useful for the separate evaluation of toxic effects on rods and cones.
Yamashita
Haruhiro
H
Drug Safety Laboratory, Taisho Pharmaceutical Co., Ltd., Saitama-shi, Saitama, Japan. h.yamashita@po.rd.taisho.co.jp
Yamasaki
Kiyo
K
Sugihara
Kazunari
K
Miyata
Hiroto
H
Tsutsumi
Shunsuke
S
Iwaki
Yoshinobu
Y
D000818:Animals; D003261:Contact Lenses; D004596:Electroretinography / Q000187:drug effects* / Q000295:instrumentation; D007452:Iodates / Q000633:toxicity*; D008027:Light; D008297:Male; D008839:Microelectrodes; D020419:Photoreceptor Cells, Vertebrate / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D012164:Retinal Diseases / Q000139:chemically induced* / Q000503:physiopathology
D007452:Iodates; C032285:sodium iodate