Neonatal exposure to monosodium glutamate alters the neurobehavioral performance of adult rats.

On days 1-15 postpartum male and female Sprague-Dawley derived CD strain pups were dosed sc with either L-glutamic acid (MSG) (2-3.5 mg/g), 13% or 0.85% saline and tested at 67 and 102 days of age. At both periods, the body weights of MSG exposed males were less than the 13% exposed isosmotic controls. MSG exposed females, however, appeared to be obese compared to their controls at 102 days and exhibited a 50% incidence of tail-automutilation. Exposure to MSG did not affect the startle responsiveness of males or females to an acoustic startle stimulus. The startle responsiveness of females to a tactile air puff stimulus was significantly depressed in amplitude at 67 and 102 days; the response on the males at 67 days of age was also decreased, but the effect was not statistically significant. Fore- and hindlimb grip strength assessments indicated that MSG exposed females, at 102 days, had greater hindlimb grip strength. Forelimb grip strength was not affected in either sex. Tail flick latencies to a thermal stimulus were significantly elevated at 67 and 102 days of age in both MSG exposed sexes. Relative to the isosmotic control group, spontaneous motor activity of MSG exposed animals was found to be consistently lower. Exposure to MSG did not, however, change the responsiveness of either sex to the motor activity stimulating effects of a d-amphetamine challenge (0.3-3 mg/kg). These results indicate that postnatal exposure to MSG produced measurable, long-term behavioral and somatic alterations in female and, to a lesser degree, male rats.