Previous studies have shown that neural stem cell transplantation has the potential to treat Parkinson's disease, but its specific mechanism of action is still unclear. Stromal cell-derived factor-1 and its receptor, chemokine receptor 4 (CXCR4), are important regulators of cell migration. We speculated that the CXCR4/stromal cell-derived factor 1 axis may be involved in the therapeutic effect of neural stem cell transplantation in the treatment of Parkinson's disease. A Parkinson's disease rat model was injected with 6-hydroxydopamine via the right ascending nigrostriatal dopaminergic pathway, and then treated with 5 mu L of neural stem cell suspension (1.5 x 10(4)/L) in the right substantia nigra. Rats were intraperitoneally injected once daily for 3 days with 1.25 mL/kg of the CXCR4 antagonist AMD3100 to observe changes after neural stem cell transplantation. Parkinson-like behavior in rats was detected using apomorphine-induced rotation. Immunofluorescence staining was used to determine the immunoreactivity of tyrosine hydroxylase, CXCR4, and stromal cell-derived factor-1 in the brain. Using quantitative real-time polymerase chain reaction, the mRNA expression of stromal cell-derived factor-1 and CXCR4 in the right substantia nigra were measured. In addition, western blot assays were performed to analyze the protein expression of stromal cell-derived factor-1 and CXCR4. Our results demonstrated that neural stem cell transplantation noticeably reduced apomorphine-induced rotation, increased the mRNA and protein expression of stromal cell-derived factor-1 and CXCR4 in the right substantia nigra, and enhanced the immunoreactivity of tyrosine hydroxylase, CXCR4, and stromal cell-derived factor-1 in the brain. Injection of AMD3100 inhibited the aforementioned effects. These findings suggest that the stromal cell-derived factor-1/CXCR4 axis may play a significant role in the therapeutic effect of neural stem cell transplantation in a rat model of Parkinson's disease.