title: Effect of L-theanine on sensorimotor gating in healthy human subjects.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Ota
authors.forename: Chisato
authors.initials: C
authors.lastname: Wakabayashi
authors.forename: Junko
authors.initials: J
authors.lastname: Matsuo
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hori
authors.forename: Kotaro
authors.initials: K
authors.lastname: Hattori
authors.forename: Daimei
authors.initials: D
authors.lastname: Sasayama
authors.forename: Toshiya
authors.initials: T
authors.lastname: Teraishi
authors.forename: Satoko
authors.initials: S
authors.lastname: Obu
authors.forename: Hayato
authors.initials: H
authors.lastname: Ozawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kunugi
mesh_terms: D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D005971:Glutamates / Q000097:blood / Q000494:pharmacology*; D006185:Habituation, Psychophysiologic / Q000187:drug effects; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D065808:Prepulse Inhibition / Q000187:drug effects*; D055139:Sensory Gating / Q000187:drug effects*
chemical_list: D005971:Glutamates; C026166:theanine
keywords: N-methyl-D-aspartate; glutamine; l-theanine (N-ethyl-l-glutamine); prepulse inhibition; sensorimotor gating