Objective:To study the gene expression pattern of neurotrophins and their receptors during neuronal differentiation of rat bone marrow stromal cells(BMSCs) in vitro and explore the mechanism of differentiation from bone marrow stromal cells into neurons. Methods:BMSCs were separated from rat bone marrow using percoll(1.073 g/L) reagent and cultured in vitro. The induction of BMSCs differentiating into neurons was used by dimethylsulfoxide(DMSO) and butylated hydroxyanisole(BHA), and the morphological changes were observed and recorded under inverted microscope. The immunofluorescence method was used to identify the differentiated BMSCs which would express neuronal marker. The expression levels of neurotrophines NGF,BDNF ,NT-3 and their high or low-affinity(TrkA,TrkB,TrkC,p75NTR) receptors before and at 2,6,12,24 and 48 h after differentiation of BMSCs were investigated by RT-PCR. Results:①Two hours after the induction,the differentiated BMSCs had morphological changes into ball-like shape with short prominence,like neurons. Immunofluorescence detection showed that the differentiated BMSCs expressed neuron marker neurofilament protein,but it was failed to detect the expression of astrocyte marker glial fibrillary acidic protein under this induction condition.②The NGF and BDNF mRNA could be detected in BMSCs during the whole stage,and the expression levels of NGF mRNA gradually decreased after induction. RT-PCR also revealed that both TrkA and TrkB expression were detected at 12 h following the onset of differentiation while not detected before differentia-tion. However no detectable expression of NT-3 and TrkC was observed in those cells either before or during differentiation. ③p75NTR appeared about 6 h after the induction of differentiation and persisted up to 12 h time point,but significantly declined and quickly diminished thereafter. Conclusion:BMSCs can be induced to differentiate into neurons in vitro. Significant changes of the expressions of neurotrophins(NT) NGF,BDNF,NT-3 and their high or low-affinity(TrkA,TrkB,TrkC,p75NTR) receptors were observed when BMSCs undergoing neuronal differentiation. The signaling pathway of NT and their receptors may take an important role in the differentiation of BMSCs into neurons.