Valproate (VPA) and its valproic acid, sodium valproate, and valproate semisodium forms are medications primarily used to treat epilepsy and bipolar disorder and prevent migraine headaches. They are useful for the prevention of seizures in those with absence seizures, partial seizures, and generalized seizures. They can be given intravenously or by mouth, and the tablet forms exist in both long- and short-acting formulations.

Source : Wikipedia

Sodium valproate has been found to have a marked anticonvulsant activity in animals - demonstrated by the various tests used to detect anti-epileptic activity.

As noted above, it's currently used to treat Epilepsyplugin-autotooltip__plain plugin-autotooltip_bigEpilepsy

"Epilepsy is a chronic noncommunicable disease of the brain that affects around 50 million people worldwide. It is characterized by recurrent seizures, which are brief episodes of involuntary movement that may involve a part of the body (partial) or the entire body (generalized) and are sometimes accompanied by loss of consciousness and control of bowel or bladder function. Seizure episodes are a result of excessive electrical discharges in a group of brain cells. Different parts of … and Migraineplugin-autotooltip__plain plugin-autotooltip_bigMigraine

"Chronic migraine has a great detrimental influence on a patient’s life, with a severe impact on socioeconomic functioning and quality of life. Chronic migraine affects 1–2% of the general population, and about 8% of patients with migraine; it usually develops from episodic migraine at an annual conversion rate of about 3%.", but its precise mechanism of action is currently unknown, though there are some speculative theories :

Its anticonvulsant effect is attributed to the blockade of voltage-dependent sodium channels and increased brain levels of gamma-aminobutyric acid (GABA). The GABA-ergic effect is also believed to contribute towards the anti-manic properties of sodium valproate.
[…]
In animals, sodium valproate raises cerebral and cerebellar levels of the inhibitory synaptic transmitter, GABA, possibly by inhibiting GABA degradative enzymes, such as GABA transaminase and/or succinic semi-aldehyde dehydrogenase and/or by inhibiting the re-uptake of GABA by neuronal cells.

Source : Gov.au