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

Abstract

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 (NaIO₃). 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/m² in rod response; background intensity and light adaptation period: 10 cd/m² 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 NaIO₃. Male rats were given NaIO₃ 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 NaIO₃ 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.

Sodium Iodate Selectively Injuries the Posterior Pole of the Retina in a Dose-Dependent Manner: Morphological and Electrophysiological Study

“…Our assumption may be confirmed by the relatively stable b-wave detected in the photopic single-flash cone response on the 1st day after the injection of the higher dose of NaIO 3 , elicited under the rod suppression conditions. The observation is consistent with a recently published report indicating that the retinal toxicity induced by a very high dose (50 mg/kg) of NaIO 3 was expressed primarily in rods, followed by cones [22]. Nevertheless, the complete RPE disintegration and subsequent acute photoreceptor degeneration observed on the 3rd day after exposure to our high concentration of NaIO 3 resulted in total suppression of both scotopic and photopic retinal function.…”

Monitoring the effect of mild ischemia with a built-in light-emitting diode contact lens electrode and a low-cost custom-made apparatus

“…Our ERG setup yielded response profiles corresponding to those obtained with commercial ERG setups and those previously described in rats by Yamashita et al (2009), who utilized the same contact electrodes. A typical normal ERG response is shown in figure 1(a).…”

“…This type of electrode has been used in humans (Suzuki et al 1998, Tsuruoka et al 2004, dogs (Kim et al 2008, Yu et al 2007, Sasaki et al 2006, Maehara et al 2005, quail (Endo et al 2008) and rabbits (Maia et al 2004). There are four reports in the literature that describe its use in rats, but with a different ERG setup (Goto et al 2002, Grozdanic et al 2003, Yoneda et al 2003, Yamashita et al 2009.…”

Morphological and functional evaluation of an animal model for the retinal degeneration induced byN-methyl-N-nitrosourea

“…One of them, sodium iodate (NaIO 3 ), is a stable retinotoxin that has been used as a RD animal model [17, 24]. However, two other study groups demonstrated a mismatch between visual function and histopathology of the retina [25, 26]. Additionally, in our preliminary test, NaIO 3 was not likely to reduce ERG responses significantly and or show apparent histopathologic findings (data not shown).…”