Modulation of human motor cortex excitability by valproate.

RATIONALE

Valproate is widely used in the treatment of epilepsy, bipolar disorder, and chronic pain disorders, but its exact mechanisms of action is still incompletely understood.

OBJECTIVES

Here we used transcranial magnetic stimulation to explore effects of a single dose of 800 mg valproate on motor cortex excitability in healthy volunteers.

METHODS

Motor threshold, peripheral maximum M-wave, cortical silent period short intracortical inhibition, intracortical facilitation, and motor evoked potential recruitment were assessed before and 1.5 h after the administration of valproate in 15 (eight male, seven female) healthy volunteers.

RESULTS

None of the measures of cortical excitability were found to be altered significantly after valproate.

CONCLUSION

These results are in line with previous findings of unaffected intracortical excitability after a single dose of valproate, suggesting that valproate's immediate in vivo actions do not resemble the effects of classic GABAergic compounds.