In rats, oral as well as i.g. administration of isolated
L-theanine led to its temporary increase in plasma, liver, brain,
and urine. This was followed by raised concentrations of
ethylamine and glutamic acid in plasma and urine, probably
due to hydrolysis of L-theanine (8,9). Moreover, L-theanine
intake increased the brain concentrations of dopamine and
g-aminobutyric acid (6), which are suggested to reduce
anxiety and improve mood (10).