Ingestion of theanine, an amino acid in tea, suppresses psychosocial stress in mice

Exp Physiol. 2013 Jan;98(1):290-303. doi: 10.1113/expphysiol.2012.065532. Epub 2012 Jun 15.


The antistress effect of theanine (γ-glutamylethylamide), an amino acid in tea, was investigated using mice that were psychosocially stressed from a conflict among male mice in conditions of confrontational housing. Two male mice were housed in the same cage separated by a partition to establish a territorial imperative. When the partition was removed, the mice were co-housed confrontationally. As a marker for the stress response, changes in the adrenal gland were studied in comparison to group-housed control mice (six mice in a cage). Significant adrenal hypertrophy was observed in mice during confrontational housing, which was developed within 24 h and persisted for at least 1 week. The size of cells in the zona fasciculata of the adrenal gland, from which glucocorticoid is mainly secreted, increased (∼1.11-fold) in mice during confrontational housing, which was accompanied by a flattened diurnal rhythm of corticosterone and ACTH in blood. The ingestion of theanine (>5 μg ml(-1)) prior to confrontational housing significantly suppressed adrenal hypertrophy. An antidepressant, paroxetin, suppressed adrenal hypertrophy in a similar manner in mice during confrontational housing. In mice that ingested theanine, behavioural depression was also suppressed, and a diurnal rhythm of corticosterone and ACTH was observed, even in mice that were undergoing confrontational housing. Furthermore, the daily dose of theanine (40 μg ml(-1)) blocked the counteracting effects of caffeine (30 μg ml(-1)) and catechin (200 μg ml(-1)). The present study demonstrated that theanine prevents and relieves psychosocial stress through the modulation of hypothalamic-pituitary-adrenal axis activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Glands / anatomy & histology
  • Adrenal Glands / drug effects
  • Adrenocorticotropic Hormone / blood
  • Animals
  • Antidepressive Agents / pharmacology
  • Caffeine / pharmacology
  • Circadian Rhythm
  • Corticosterone / blood
  • Glutamates / pharmacology*
  • Housing, Animal
  • Hypertrophy
  • Hypothalamo-Hypophyseal System / drug effects
  • Hypothalamo-Hypophyseal System / physiology
  • Male
  • Mice
  • Organ Size / drug effects
  • Paroxetine / pharmacology
  • Pituitary-Adrenal System / drug effects
  • Pituitary-Adrenal System / physiology
  • Social Dominance*
  • Stress, Psychological / drug therapy*
  • Tea / chemistry


  • Antidepressive Agents
  • Glutamates
  • Tea
  • Caffeine
  • Paroxetine
  • theanine
  • Adrenocorticotropic Hormone
  • Corticosterone