Monosodium-L-glutamate-induced convulsions--I. Differences in seizure pattern and duration of effect as a function of age in rats.

Convulsive activity in 3, 10, 60 and 180-day old Sprague-Dawley rats was studied following the i.p. administration of 4 mg g-1 of commercial MSG. The latency period increased with the age of the animals while the duration of the convulsive period was longer in younger animals and shorter in 60-day old rats. Convulsions were predominantly tonic in 3 and 10-day old rats, tonic-clonic in 60-day old rats, and predominantly clonic in 180-day old animals. The severity of the convulsions and death incidence increased progressively with age. Animals injected either with sodium chloride equimolar to MSG or physiological saline solution showed no convulsive activity. The effects of MSG without trace metals were no different from those produced by commercial MSG.