Neural stem cells are self-renew multipotential cells in the brain,which have the potential to differentiate into neurons,astrocytes and oligodendrocytes.Microglia are part of the mononuclear phagocyte system in the parenchyma of the CNS and have long been characterized by their immune function in the nervous system.Until present,very few reports are related to how microglia function on differentiation of neural stem cells.Our study used co-culture of primary microglia and neural stem cells of rat to detecte effects of microglia on differentiation of neural stem cells.By applying transwell insert,microglia and neural stem cells had been co-cultured for 1,3 and 5 d,3 d after co-culture,Western Blotting,RT-PCR and immunocytochemical analysis revealed that Nestin and Map-2 expression was decreased compared with control,while GFAP expression were increased.These data suggested that co-culture with microglia enhanced neural stem cells differentiating into astrocytes.