Objective      To determine the effect of sodium valproate (VPA) on the proliferation and cell cycle in adult female rat spinal neural stem cells (NSCs)．       Methods      Cell proliferation was assessed by CCK-8 assay after the cells were treated with VPA at different concentrations of 10

-5

10

-4

10

-3

10

-2

10

-1

1 or 10 mmol/L for 0

24

48 or 72 h. After NSCs were treated with VPA at a dose of 10

-5

and 1 mmol/L for 48 h

cell cycle was analyzed by flow cytometry and the expression of p21(cyclin-dependent kinase inhibitor) was detected by PCR and Western blot analysis.       Results      CCK-8 staining colorimetry showed that the proliferation of NSCs was markedly inhibited in a time-dependent manner when the concentration of VPA was more than 10

-5

mmol/L. Flow cytometry indicated more cultured NSCs were arrested in the G

0

/G

1

phase and fewer at the S phase after being treated with VPA

which indicated that VPA arrested the transition of NSCs from G

0

/G

1

phase to S phase. PCR and Western blot analysis indicated that VPA enhanced the expression of p21 at mRNA and protein levels(

P

<

0.05)．       Conclusion      VPA may arrest NSCs at G

0

/G

1

by increasing the expression of p21

and then finally inhibit the proliferation of NSCs．