Microarray analysis of rat brain gene expression after chronic administration of sodium valproate

Valproic acid has been used to treat mania and bipolar disorder, but its mechanism of action is not agreed on. We used rat genome U34A Affymetrix oligonucleotide microarrays, containing 8799 known probesets, to determine the effect of 30-day daily intraperitoneal administration of valproate (200 mg/kg) on rat brain gene expression. We found 87 down-regulated genes and 34 up-regulated genes of at least a 1.4-fold change in valproate-treated compared to control rats. The experiments were done on five independent samples for each group, each in duplicate. The genes affected are known to be involved in a variety of pathways, including synaptic transmission, ion channels and transport, G-protein signaling, lipid, glucose and aminoacid metabolism, transcriptional and translational regulation, phosphoinositol cycle, protein kinases and phosphatases, and apoptosis. Our results suggest that the therapeutic effect of valproate may involve the modulation of multiple signaling pathways.