Green tea component, (-)-epigallocatechin gallate, but not L-theanine, has sedative effects in chick under acute stress conditions

Tea has two major components that may act on the brain to reduce stress. One is (-)-epigallocatechin gallate (EGCG), which we have recently shown to cause a sedative effect through gamma-aminobutyric acid (GABA) _A receptors in the brain of neonatal chicks, and another is L-theanine that is shown to induce a feeling of relaxation in humans. The purpose of the present study was to compare the effects of EGCG and theanine on stress in neonatal chicks. Intracerebroventricular (i.c.v.) injection of EGCG (109 nmol) attenuated the increase in vocalization and spontaneous activity that is observed during a 10 min social-isolation stress. Consistent with this result, EGCG decreased the time for active wakefulness while increasing that of sleep-like behavior. L-Theanine (109 nmol) had no effect on these behaviors. It was concluded that central EGCG, but not L-theanine, plays a role in reducing stress associated with social isolation in our model using neonatal chicks.