Valerenic acid and Valeriana officinalis extracts delay onset of Pentylenetetrazole (PTZ)-Induced seizures in adult Danio rerio (Zebrafish)

BACKGROUND Anticonvulsant properties have been attributed to extracts of the herbal medicine Valeriana officinalis. Our aims were to examine the anticonvulsant properties of valerenic acid and valerian extracts and to determine whether valerian preparations interact with the activity of other anti-epileptic drugs (phenytoin or clonazepam). To achieve these goals, we validated the adult zebrafish, Danio rerio, as an animal model for studying anticonvulsant drugs. METHODS All drug treatments were administered by immersion in water containing the drug. For assays of anticonvulsant activity, zebrafish were pretreated with: anti-epileptic drugs, valerenic acid, aqueous or ethanolic valerian extracts, or mixtures (phenytoin or clonazepam with valerenic acid or valerian extracts). Seizures were then induced with pentylenetetrazole (PTZ). A behavioral scale was developed for scoring PTZ-induced seizures in adult zebrafish. The seizure latency was evaluated for all pretreatments and control, untreated fish. Valerenic acid and both aqueous and ethanolic extracts of valerian root were also evaluated for their ability to improve survival after pentylenetetrazole-challenge. The assay was validated by comparison with well-studied anticonvulsant drugs (phenytoin, clonazepam, gabapentin and valproate). One-way ANOVA followed by Tukey post-hoc test was performed, using a p < 0.05 level of significance. All treatments were compared with the untreated animals and with the other pretreatments. RESULTS After exposure to pentylenetetrazole, zebrafish exhibited a series of stereotypical behaviors prior to the appearance of clonic-like movements--convulsions. Both valerenic acid and valerian extracts (aqueous and ethanolic) significantly extended the latency period to the onset of seizure (convulsion) in adult zebrafish. The ethanolic valerian extract was a more potent anticonvulsant than the aqueous extract. Valerenic acid and both valerian extracts interacted synergistically with clonazepam to extended the latency period to the onset of seizure. Phenytoin showed interaction only with the ethanolic valerian extracts. CONCLUSIONS Valerenic acid and valerian extracts have anticonvulsant properties in adult zebrafish. Valerian extracts markedly enhanced the anticonvulsant effect of both clonazepam and phenytoin, and could contribute to therapy of epileptic patients.