[The effects of neonatal monosodium glutamate treatment on sex-odor attractivity and approach behavior in rats].

The neurotoxic effects of monosodium glutamate (MSG) on certain parts of the central nervous system (CNS) and endocrine functions are well documented. MSG-treated rats exhibit stunted growth, obesity and decrease in sexual behavior. The present study was designed to evaluate how neonatal administration of MSG affects sex-odor attractivity and approach behavior, and to investigate factors limiting copulation in MSG-treated rats. In this experiment, subcutaneous injections of MSG (400 mg MSG/ml normal saline/0.1 Kg B.W.) were given to Long-Evans pups on days 1 and 3 after birth, whereas the control groups received normal saline injections of equal volume (1 ml/0.1 kg B.W.). When the rats were 3 months old, sex-odor attractivity and approach behavior were tested. Two points were displayed by MSG-treated rats: (a) attenuated the attractivity of sex-odor. (b) decreased performance of sexual approach to partners. From our results and those of a previous study, we suggest that the deterioration of sex-odor attractivity and approach behavior to partners is attributed to a decline in sexual hormones. Furthermore, we concluded that this decrease in behaviors is to some extent responsible for reduced copulatory behavior.