(-)-Epigallocatechin gallate (EGCG) has a sedative effect acting through γ-aminobutyric acid (GABA)A receptors in the brain, but it is unclear what structural components of the molecule are necessary for its action. To investigate the necessity of the galloyl group on the sedation induced by EGCG, the effect of EGCG was compared with (-)-epigallocatechin (EGC) in which the galloyl group is removed from EGCG. Intracerebroventricular (i.c.v.) injection of EGC, as well as EGCG, induced, and the effect of EGC were blocked by the GABAA receptor antagonist picrotoxin. It is concluded that catechins have a sedative effect acting through GABAA receptors under an acute stress condition irrespective of the presence of the galloyl group.
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