Corn feeding during development induces changes in the number of serotonergic neurons in the raphe nuclei

Serotonin (5-HT) plays a trophic role during brain development; chronic changes in cerebral concentration of this neurotransmitter during the critical stage of development can produce severe damage in the formation of the neural circuits. For the present work a hypoproteic (HYP) diet based on corn (CORN) meal which is deficient in tryptophan (TRY) was given to rats before and during pregnancy, which continued to the offspring until they reached 60 days of age. An isocaloric but hypoproteic diet containing normal amount of TRY, and normal chow (Ch) Purina were given with the same scheme to two groups of rats considered as controls. 5-HT immunohistochemistry was revealed by avidin-biotin complex (ABC) method to quantify serotonergic nerve cells in the nine raphe nuclei. The number of cells immunoreactive to 5-HT immunoreactive (5-HTir) were quantified by means of stereological analysis. Results demonstrated a significant variation in 5-HT expression in the raphe nuclei. Thus, a significant reduction in the number of 5-HTir cells in the rostral raphe nuclei was seen at all ages studied in the animals fed the corn diet, compared to data obtained from the control groups. This decrease was more evident between the postnatal ages of 30 and 60 days. It is concluded that the variations in the available TRY affect the brain cells producing 5-HT and the innervation of their target areas.