(-)-Epigallocatethin-3-O-gallate counteracts caffeine-induced hyperactivity: evidence of dopaminergic blockade.
This experiment was designed to know whether (-)-epigallocatethin-3-O-gallate (EGCG) counteracts caffeine-induced hyperactivity, and its potential mechanisms in mice. EGCG inhibited methamphetamine-induced, cocaine-induced and caffeine-induced horizontal hyperlocomotion and rearing activity. EGCG also inhibited hyperlocomotion and rearing activity induced by apomorphine, a D1/D2-like agonist. Moreover, EGCG inhibited climbing behavior, a typical stereotyped behavior induced by stimulation of dopamine receptors through the activation of those receptors by apomorphine. From this experiment, we suggest that EGCG inhibits hyperactivity induced by psychostimulants including caffeine, in part by modulating dopaminergic transmission, and these inhibitory effects of EGCG counteract the stimulant actions of caffeine in green tea.