Ingestion of theanine, an amino acid in tea, suppresses psychosocial stress in mice.
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.
Laboratory of Bioorganic Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. unno@u-shizuoka-ken.ac.jp
Keiko
K
Unno
Kazuaki
K
Iguchi
Naoki
N
Tanida
Keisuke
K
Fujitani
Nina
N
Takamori
Hiroyuki
H
Yamamoto
Naoto
N
Ishii
Hiroko
H
Nagano
Takashi
T
Nagashima
Ayane
A
Hara
Kayoko
K
Shimoi
Minoru
M
Hoshino
D000311:Adrenal Glands / Q000033:anatomy & histology / Q000187:drug effects; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood; D005971:Glutamates / Q000494:pharmacology*; D006799:Housing, Animal; D006984:Hypertrophy; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D009929:Organ Size / Q000187:drug effects; D017374:Paroxetine / Q000494:pharmacology; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D012930:Social Dominance; D013315:Stress, Psychological / Q000188:drug therapy*; D013662:Tea / Q000737:chemistry
D000928:Antidepressive Agents; D005971:Glutamates; D013662:Tea; D002110:Caffeine; D017374:Paroxetine; C026166:theanine; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone