Objective To study the effect of extracellular signal-regulated kinase 1/2 (ERK1/2) signal transduction pathway on differentiation of rat bone marrow stroma cells (BMSCs) into neuron-like cells induced by Salvia miltiorrhiza.Methods Rat BMSCs were isolated and purified in vitro by whole bone marrow method.At the third passage,BMSCs were induced and assigned into 3 groups:control group (group A),Salvia miltiorrhiza treatment group (group B) and PD98059 (ERK1/2 specific inhibitor) treatment group (group C).Morphology was observed.Neuron-specific enolase (NSE) and Nestin protein expressions were detected by immunohistochemistry.The mRNA expressions of NSE and Nestin were detected by PCR.Results Following 1 h of induction,no significant changes in cell morphology was noted in group A; cells in group B showed obvious changes,with some cone-shaped and with an increased number of cells which stretched and had similar shape with neurons,and cells stretched much more obviously over time and connected to each other; the number of total cells,neuron-like cells and neuritis in group C was decreased as compared with those in group B.As compared with group A and group C,group B had significantly higher NSE-and Nestin-positive rates,and higher NSE and Nestin mRNA expressions 5 h after treatment (P＜0.05).Conclusions Salvia miltiorrhiza can promote the differentiation of BMSCs into neuron-like cells.ERK1/2 specific inhibitor PD98059 can resist Salvia miltiorrhiza effects,indicating that ERK1/2 is the key signal pathway of the promotion effects of Salvia miltiorrhiza on differentiation of BMSCs into neuron-like cells.