Objective    To explore the effects of triiodothyronine (T

3

) on the differentiation of neural stem cells into oligodendrocytes and the changes of transcriptional factor

inhibitor of DNA binding-2 (Id2).     Methods    Neural stem cells from subventricular zone of new born Wistar rats were cultured in vitro

and the cell types and ratio of differentiated cells were observed after T

3

treatment as well as the changes of Id2 expression at different stages.     Results    The expressions of Id2 were strong in normal undifferentiated neural stem cells

and decreased at 2 h and

12 h after differentiation

then increased gradually again. T

3

accelerated the differentiation of neural stem cells

and the expression levels of Id2 were higher than those of the normal group. At the same time

the quantity of oligodendrocytes was increased while the quantity of astrocytes was decreased.     Conclusion     T

3

stimulates oligodendrocyte formation and inhibits astrocyte formation from neural stem cells

possibly through increasing Id2 expressions.