Effect of L-theanine on sensorimotor gating in healthy human subjects

Psychiatry Clin Neurosci. 2014 May;68(5):337-43. doi: 10.1111/pcn.12134. Epub 2013 Dec 25.


Aim: l-Theanine (N-ethyl-l-glutamine) is an amino acid uniquely found in green tea. Growing evidence has suggested the possible effects of l-theanine on cognition. Previously, we found that l-theanine attenuates MK-801-induced deficit in prepulse inhibition (PPI) in mice. In this study, we examined the effect of l-theanine in increasing the PPI in healthy humans.

Methods: The subjects were 14 healthy adults who underwent PPI testing as a measure of sensorimotor gating 90 min after an oral intake of l-theanine (0, 200, 400, or 600 mg). PPI tests were done by examiners who were blind to the dose.

Results: The administration of 200 mg of l-theanine and that of 400 mg, but not 600 mg, significantly increased the % PPI compared to the baseline (0 mg). There was no significant relation between the dose of l-theanine and the startle magnitude or the habituation of startle response. The plasma concentrations of l-theanine correlated with the dose of l-theanine.

Conclusion: The observed effect with 200-400 mg of l-theanine on PPI suggested that l-theanine at a particular dose range increases sensorimotor gating in humans.

Keywords: N-methyl-D-aspartate; glutamine; l-theanine (N-ethyl-l-glutamine); prepulse inhibition; sensorimotor gating.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Dose-Response Relationship, Drug
  • Female
  • Glutamates / blood
  • Glutamates / pharmacology*
  • Habituation, Psychophysiologic / drug effects
  • Healthy Volunteers
  • Humans
  • Male
  • Prepulse Inhibition / drug effects*
  • Sensory Gating / drug effects*


  • Glutamates
  • theanine