It is well known that parenteral neonatal monosodium glutamate (MSG) administration has toxic effects on arcuate nucleus neurons, leading to significant brain lesions, neuroendocrine disturbances and obesity (1-3). The present study was undertaken to investigate whether oral MSG administration was able to produce the same effect. Thirty pregnant Wistar rats were separated in three groups; the first two groups received specific diets containing 0, (control group, CT group) or 4 g MSG/Kg BW, (oral treatment group, OT group) from day 14th of pregnancy onwards. The third group of mothers received standard rat chow, but their offspring was neonatally injected with MSG (4mg/g BW) on alternate days for the first 10 postnatal days (day 2, 4, 6, 8, 10), (parenteral treatment group, PT group). The other groups received saline injections on the same days. After weaning, MSG feeding was continued in the first two groups at the same concentrations in the offspring until 6 months of life. Body weight of animals as well as food intake were measure periodically. Half of the pups were sacrificed at 1 month and the rest at the 6 month of life. Blood samples were collected for Leptin radioimmunoassay determination. Hypothalamus were collected as well for neuropeptide Y (NPY) and Leptin receptor (R-leptin) mRNA expression determinations using real time PCR. Even though no changes were observed in body weight in PT group with respect to control group at one month life, at six months life, AP group showed lower body weight and body weight gain than the other two groups (p<0.001). By contrast, the group of rats treated orally with MSG 4g/Kg BW presented lower body weight than the other two groups at one month of life (p<0.001), but at six months there were no differences in body weight and body weight gain between this group and CT. In addition, food intake was significantly augmented in OT group respect to CT and PT groups (p<0,01). Plasma Leptin levels were not significantly modified in orally treated group with respect to control at 1 and 6 month of life. Nevertheless, this hormone was markedly increased in PT group at 1 month (p<0.05) and 6 month (p<0.01) of life. At six month life, both groups, orally and parenterally MSG treated groups showed significantly reduced expression levels of NPY and R-leptin mRNA with respect to control group (p<0.05). A In conclusion, all these data support that MSG administered orally is able to produce disturbances in nutritional and endocrine parameters in the same way as parenteral administration.