study in rats, by others, 5-methoxytryptophan treated damns gave birth to pups with cytoarchitectonic derangement in presubicular cortex. To ascertain the effects of 5-HT in cortical neuronal migration experimental animals were fed a low tryptophan diet (LT). With this diet was intended to lower 5-HT levels through reduction in tryptophan availability, necessary for 5-HT synthesis. The dietary intake is men and rodents only source of tryptophan. Wistar pregnant rats and their litters were used. They were divided in three groups: one group was fed LT through gestation and lactation, other was fed with LT diet with added tryptophan into the formulation (LTT) and the last group was fed with the standard 18% protein diet. Every diet was continued to feed pups after weaning. Rats were sacrificed at postnatal days (P) 0, 20 and 30. Brains were processed for tryptophan hydroxylase immunohistochemistry (P0), Golgi (P30) and Nissl (P20) staining and photodocumented. Serotonin content in the brainwasmeasured at P0, P20 and P30 by HPLC of brain extracts. In animals fed with LT cytoarchitectonic derangement was found in neocortex and hippocampus allocortex, visualized at P20 and P30. These results suggest that a 5-HT level set point at ontogeny is essential in events such as cortical neuronal migration.