RESUMO
Objective To explore the development of nitrergic neurons in the tongue of human fetus. Methods Using histochemical method of NADPH\|diaphorase, the differentiation, migration and development of the nitrergic neurons in the tongue of human fetus were studied. Results At the fourth month of the gestation, the round cells of epithelial tissue in tongue differentiated into fusiform nitrergic nerve cells, which moved from the epithelial tissue to subepithelial and muscular tissue. The bodies of nitrergic neurons were small, the positive reaction of nitric oxide synthase(NOS) was weak. The development of the process of nitrergic neurons might be divided into two phases:The first phase, the growth and development phase, occured from the fourth to the seventh month, the somatic size enlarged gradually, the numbers increased, the positive reaction of NOS increased gradually and reached its peak at the seventh month. The morphology of neurons was characterized by the development from the fusiform form to the tadpole form and then a diversity of shape. The second phase, the maturation phase, denoted the eighth to tenth month, the bodies of nitrergic neurons were obviously enlarged, the staining intensity of NOS was increased. The nitrergic neurons were scattered in the subepithelial layer and muscular tissue and the typical ganglionic cells were observed. Conclusion Nitrergic neurons of tongue originate from its epithelial tissue at the time of early fetal development. By the differentiation, migration, multiplication, growth and maturation, mature nitrergic neurons are formed. [