Effects of a central stimulant substance isolated from the sea anemone Stoichactis kenti on brain monoamines of the mouse

An active substance, polypeptide in chemical nature, causing central stimulant activity in mice has been isolated from a sea anemone. Signs of central nervous stimulatory activity produced by this substance included fighting episodes, increased motor activity and clonic convulsions. The active substance produced significant decreases in brain norepinephrine concentration both at the ED 50 (6.4 mg/kg) and the maximum effective dose (9.3 mg/kg) during the stimulation period. Brain dopamine concentration was significantly decreased by the active substance at the ED 50 dose whereas brain serotonin concentration was not affected. The ED 50 dose of the active substance significantly inhibited the re-uptake of norepinephrine during the stimulation period and elevated hormetanephrine levels. These results suggest that the active substance causes central stimulation by releasing active norepinephrine from functional pools and inhibiting its re-uptake, thus making more norepinephrine available at a adrenoceptors. It is probable that brain dopamine plays a minor role in this stimulant action of the active substance.