Visually evoked potentials as an early indicator of acrylamide-induced visual dysfunction in rats

Humans rely heavily on visual function to gather information, and loss of vision has a significant impact on quality of life. However, it is difficult to quantitatively evaluate the effects of chemical compounds on visual function in toxicity studies using animals (such as OECD guideline studies). Consequently, evaluation including ophthalmological and histopathological examinations has played a major role to date. Visually evoked potential (VEP) is a type of brain wave that reflects the activity of the entire visual pathway, including the retina, optic nerve, and visual cortex. We investigated whether VEP could detect the effects of acrylamide, a toxicant known to affect peripheral nerves, on visual function. Acrylamide was administered to rats via drinking water at concentrations of 0 (control) and 200 ppm for 4 weeks, and electroretinograms (ERGs) and VEPs were recorded at weeks 0, 2, and 4. After the 4-week treatment period, the eyes and optic nerves were examined by light microscope. Acrylamide exposure significantly delayed VEP latency, while no effects were observed on the retina and optic nerve by ERG or histopathology. A significant decrease in grip strength in the hindlimbs and degeneration of sciatic nerve fibers were observed in the acrylamide-treated group, indicating that acrylamide damaged peripheral nerves. In conclusion, our study demonstrated that VEP can detect the effects of acrylamide on visual function earlier than histopathological examination, suggesting that VEP could be useful for detecting early-phase effects of chemical compounds on visual function and for evaluating whether morphological changes observed in toxicity studies are toxicologically significant.