In attempts to study drug-induced visual impairment, we measured the visual threshold in rats using the shuttle box method. Male Wistar rats were trained to avoid an electric shock during the presentation of conditioned stimuli (light and/or tone). The percent of avoidance was significantly decreased in rats suffering, from valinomycin-induced cataracts or alkaline-burn on the cornea when light alone was used as the conditioned stimulus. However, these rats could respond correctly to the conditioned stimulus of tone. On the other hand, rats whose eyes were impaired before conditioning could acquire the avoidance response to the presentation of both tone and light. However, when these conditioned stimuli were presented separately, the animals could not avoid the shock in the presentation of light. From these results, it appears that this method is easily applied, and the visual impairment of many rats can be detected over a short period. This approach may be a useful method for screening visual toxicity of drugs.
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