Locomotor and learning deficits in adult rats exposed to monosodium-L-glutamate during early life.

Neonatal administration of neurotoxic doses of monosodium-L-glutamate (MSG) to rats causes neuronal necrosis of the hypothalamus along with behavioral abnormalities. In the present study the behavioral effects in rats treated with subneurotoxic doses of MSG (2 mg/g, p.o., for 10 days) at the weaned stage were investigated at day 90 post-dosing. The MSG-treated rats did not show significant changes in any of the components of spontaneous locomotor activity but, after apomorphine challenge, marked decreases in the distance travelled, ambulatory and stereotypic times, and the number of stereotypic movements with an increase in the resting time were observed. Significant decrease in the active avoidance learning performance was observed in the MSG-treated rats in the learning (acquisition) phase without any changes in the extinction and relearning phases. The results indicate that exposure to MSG in early life in rats could lead to subtle behavioral aberrations in late adulthood.