Visual performance in monosodium glutamate-treated rats

The purpose of this study was to examine the effect of monosodium glutamate on the visual performance in rats. The Wistar strain of neonatal rats were injected subcutaneously with a solution of the glutamate at doses of 1 or 2 or 4 mg/gm body weight on days 2, 4, 6, 8 and 10 postnatally. Control rats received an injection of physiological saline. At 1, 2 and 3 months of age, the rats were tested for visual performance (brightness discrimination, pattern discrimination and visual acuity). As a result, the 4 mg/gm glutamate treatment was observed to impair brightness discrimination performance at 1 month of age as compared to the control animals. This impairment was also observed in animals at 2 and 3 months as compared, in addition, to the values in other doses of glutamate treatment. Pattern discrimination performance in every group of animals was at the same level at 1 month of age. However, at 2 months of age, the performance in the 2- and 4 mg/gm glutamate-treated groups was lower than those in the control group. This comparison was more pronounced at 3 months of age. Visual acuity performance results were quite the same as the pattern discrimination performance at all ages of animals. In conclusion, glutamate treatment was shown to cause dose-dependent deficit in visual performance and this may reflect impairment of visual organs and brain function.