Nurrl is a member of the nuclear receptor superfamily and is a regulatory factor of differentiation, migration, and maturation of mesencephalic dopaminergic neurons.The present study was designed to observe the dynamic changes of protein expression of Nurrl as well as its relationship with proliferating cell nuclear antigen (PCNA) in the rat brain and spinal cord development, and to investigate the significance of Nurrl in differentiation and migration of nerve cells.Paraffin-embedded sections, immunohistochemistry, immunohistochemical double staining and westem blot were adopted.The results demonstrated that in embryo development, the Nurrl-positive cells increased apparently and migrated gradually far from the lateral ventricle.In postnatal rats, the positive cells surrounding the lateral ventricle decreased remarkably.The expression of Nurrl in the cerebral cortex peaked at days P1-P5, decreased obviously along with maturation of the cells and became rare in matured cerebral cortex.