Little is known about whether tamoxifen (TAM) can affect resting state microglia apoptosis and about the cellular mechanism that may account for this.To explore this question,we incubated the microglia cell line BV-2 cells with TAM at different concentrations.Cell viability was assessed by the MTT assay,and flow cytometric analysis was performed to detect the cell apoptosis rate.Furthermore,mitochondrial membrane potential (△ψm) was tested by flow cytometry,and Bax,Bcl-2,Fas,and Fas-L expression was detected by Western blot.The results demonstrated that TAM decreased cell viability and induced apoptosis of BV-2 cells in a concentration- and time-dependent manner.In addition,disruption of Δψm was followed by up-regulated expression of pro-apoptotic Bax,Fas and Fas-L,and down-regulated expression of anti-apoptotic Bcl-2.These results indicate that TAM may induce apoptosis of BV-2 cells through both mitochondria- and death receptor-mediated pathways.