Long-term effects on behaviour after postnatal treatment with monosodium-L-glutamate.

22 rats of the Long-Evans strain (11 males and 11 females) were treated from the first to the eleventh postnatal day (pd) with daily subcutaneous injections of 4 mg/g body weight monosodium-L-glutamate (MSG) in aqua dest. Further 11 males and 7 females were used as controls and received isotonic NaCl-solution on the same days. The neurological investigation after 1 month revealed no difference between MSG-treated or untreated controls. All MSG treated rats were retarded in growth and body weight development. None of them died from the treatment. During 10 min exposure in a 60 x 75 x 22 cm open field (OF) we found higher rates of infrared beam crossing on pd 12-14, more rearing on pd 12, 16 and 32 and less immobility of MSG rats. Latencies of immobility and grooming were significantly prolonged versus controls. We found no essential differences of MSG effects between males and females. At the age of 4 months the ability for active avoidance was tested. When they could find the escape possibility, then the escape velocity was like in controls. But MSG rats had troubles to find this possibility at the beginning of a Y-maze training and during alternation of the goal (brightness discrimination). They never found the escape and avoidance possibility in a vertical jump test.