We studied the effects of histone deacetylase inhibitor that stimulates transcriptional activity via histone hyperacetylation on memory formation. Sodium butyrate and sodium valproate enhanced memory in chicks following "weak" training with memory transfer into long-term state. Quantitative analysis of c-Fos and ZENK transcriptional factor gene expression in six structures of chick brain revealed induction of these genes in the structures involved in this type of learning. Sodium valproate administration did not increase this induction, but even reduced it. These findings suggest that sodium butyrate and sodium valproate exert cognitive stimulating action in the "weak" memory formation paradigm, and that this effect is not mediated via enhanced expression of transcriptional factors, which are traditionally considered as "molecular switcher" for memory transfer into long-term state.