The effect of valproic acid on 5-hydroxytryptamine and 5-hydroxyindoleacetic acid concentration in hippocampal dialysates in vivo.

The effect of valproic acid (100, 200 and 400 mg/kg i.p.) on extracellular 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) has been studied using intracerebral microdialysis of the ventral hippocampus. Valproate caused a dose-dependent increase in dialysate 5-HT, but in contrast no effect on 5-HIAA level was observed. These findings are considered with regard to a possible role of 5-HT in mediating the anticonvulsant action of valproate.