Treatment with both lithium and valproate had an additive effect on the surface GluR1 expression of hippocampal neurons. After being cultured for 10 d, hippocampal neurons were treated with lithium only, valproate only, and lithium plus valproate for 4 d. Surface GluR1 was determined by biotinylation assay. Samples were pooled from three independent experiments, with n of 9-12 (ANOVA; #,**p < 0.05). Con, Control.