Differentiation of neural stem cells into tyrosine hydroxylase (TH)-expressing cells was studied by cell transplantation into the various brain regions of rats that had received 6-hydroxydopamine lesion of the nigrostriatal pathway. Approximately 13.6-16.1% of survived precursor cells acquired neuronal-like features by expressing the neuronal marker doublecortin. Similarly, 20.7-25.7% of survived precursor cells differentiated into astrocytes following transplantation. Immunohistochemical analysis revealed that a fraction of the grafted precursor cells in the anterior part of the medial forebrain bundle (MFB), but not in the striatum and the substantia nigra of the lesioned side, showed strong TH immunoreactivity. This suggests that MFB is more permissive for induction of TH to the striatal precursor cells in vivo. The results further exemplify the potential of neural stem cells and the property of site-specific differentiation when the cells were transplanted to the dopaminergic system of the adult brain.