Theanine is an amino acid commonly found in tea infusions of Camellia sinensis. Theanine is related to glutamine, and can cross the blood-brain barrier. Because it can enter the brain, theanine has psychoactive properties. Theanine has been shown to reduce mental and physical stress and may produce feelings of relaxation. Theanine is speculated to produce these effects by increasing the level of gamma-aminobutyric acid GABA production. Theanine increases brain serotonin, dopamine, GABA levels and has micromolar affinities for AMPA, Kainate and NMDA receptors. It has also been found that injecting spontaneously hypertensive mice with theanine significantly lowered levels of 5-hydroxyindole in the brain. Researchers also speculate that it may inhibit glutamic acid excitotoxicity. Theanine also promotes alpha wave production in the brain. Studies on test rats have shown that even repeated, extremely high doses of theanine cause little to no harmful psychological or physical effects. L-the
