Inhibitory Effects of Valproate on Impairment of Y-maze Alternation Behavior Induced by Repeated Electroconvulsive Seizures and c-Fos Protein Levels in Rat Brains

We previously showed that inhibition of repeated electroconvulsive shock (ECS)-induced seizures through 7-day administration of anti-epileptic drugs suppressed the impairment of spontaneous alternation behavior in the Y-maze test in rats. To clarify the precise mechanism(s), we investigated the effect of valproate on such impairment and examined the levels of brain-derived neurotrophic factor (BDNF) and c-Fos protein in the prefrontal cortex and the hippocampus 24h after the last administration of ECS. Seven-day intraperitoneal (i.p.) administration of valproate (400mg/kg) suppressed the impairment of spontaneous alternation behavior. Repeated ECS increased the BDNF protein levels in the hippocampus and prefrontal cortex in the presence or absence of valproate, indicating that the increase in BDNF protein levels resulted from electrical stimulation. c-Fos protein levels were significantly decreased in the hippocampal dentate gyrus after repeated ECS, but valproate had no significant effect on decreased c-Fos protein levels. Valproate＋ECS significantly increased the c-Fos protein levels of the prefrontal cortex compared with the ECS group. These findings suggest that the inhibitory effect of valproate on repeated ECS-induced impairment of spontaneous alternation behavior may be linked to the prefrontal cortex.