Behavioural pharmacology of polygalasaponins indicates potential antipsychotic efficacy

Polygalasaponins were extracted from a plant (Polygala tenuifolia Willdenow) that has been prescribed for hundreds of years to treat psychotic illnesses in Korean traditional medicine. Previous in vitro binding studies suggested a potential mechanism for its antipsychotic action, as polygalasaponin was shown to have an affinity for both dopamine and serotonin receptors [Psychopharmacol. Bull. 31 (1995) 139.]. In the present study we have investigated the functional in vivo actions of this material in tests that are predictive of dopamine and serotonin antagonist activities. Polygalasaponin (25-500 mg/kg) was shown to produce a dose-related reduction in the apomorphine-induced climbing behaviour (minimum effective dose [ED(min)] 25 mg/kg ip, 250 mg/kg sc and po), the 5-hydroxytryptamine (5-HTP)-induced serotonin syndrome (ED(min) 50 mg/kg ip) and the MK-801-induced hyperactivity (ED(min) 25 mg/kg ip) in mice. This compound also reduced the cocaine-induced hyperactivity (ED(min) 25 mg/kg ip) in rats. These results demonstrated that polygalasaponin has dopamine and serotonin receptor antagonist properties in vivo. This might suggest its possible utility as an antipsychotic agent.