VPA decreased the level of IκB. (A) The level of NF-κB p65, NF-κB p50 and IκBα were measured by Western blot. (B) Densitometric quantification of the level of IκBα (n = 7). (C) Immunocytochemical staining of IκBα in NPCs. NPCs were stained with an antibody against IκBα and co-stained with DAPI. Results are mean ± S.E.M. **P < 0.01 and ***P < 0.001 vs. control. Scale bar represents 50 μm.