Research Database

Author: Yokogoshi H, and Kobayashi M, and Mochizuki M, and Terashima T

Theanine, r-glutamylethylamide, is one of the major components of amino acids in Japanese green tea. Effect of theanine on brain amino acids and monoamines, and the striatal release of dopamine (DA) was investigated. Determination of amino acids in the brain after the intragastric administration of theanine showed that theanine was incorporated into brain through blood-brain barrier via leucine-preferring transport system. The concentrations of norepinephrine, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5HIAA) in the brain regions were unaffected by the theanine administration except in striatum. Theanine administration caused significant increases in serotonin and/or DA concentrations in the brain, especially in striatum, hypothalamus and hippocampus. Direct administration of theanine into brain striatum by microinjection caused a significant increase of DA release in a dose-dependent manner. Microdialysis of brain with calcium-free Ringer buffer attenuated the theanine-induced DA release. Pretreatment with the Ringer buffer containing an antagonist of non-NMDA (N-methyl-D-aspartate) glutamate receptor, MK-801, for 1 hr did not change the significant increase of DA release induced by theanine. However, in the case of pretreatment with AP-5, (+/-)-2-amino-5-phosphonopentanoic acid; antagonist of NMDA glutamate receptor, the theanine-induced DA release from striatum was significantly inhibited. These results suggest that theanine might affect the metabolism and/or the release of some neurotransmitters in the brain, such as DA.

 

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Author: Terashima T, and Takido J, and Yokogoshi H

Author: RYOHEI KIMURA, and TOSHIRO MURATA

Theanine (N-ethylglutamine), a flavourous constituent of tea leaves, was studied in respect of the influence on the central nervous system in mice.
Theanine was shown to inhibit the convulsive action of caffeine, but was ineffective against pentetrazole, picrotoxin, strychnine, pipradrol and bemegride as well as L-glutamine. Neither theanine nor L-glutamine effected on the prolongation of the sleeping time after the injection of hexobarbital sodium in mice. Using 14C-labeled theanine, it was found that the intraperitoneally administered theanine was taken up by brain tissue with out undergoing the metabolic changes in a 30minutes. The intracerebral level of γaminobutyric acid was shown to increase significantly at 30minutes following the intraperitoneal administration of theanine in mice.

 

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Author: Kim Zarse and Saskia Jabin and Michael Ristow

Author: Tsuge H, and Sano S, and Hayakawa T, and Kakuda T, and Unno T

A Combination of Green Tea Extract and l-Theanine Improves Memory and Attention in Subjects with Mild Cognitive Impairment: A Double-Blind Placebo-Controlled Study

Author: Sang-Ki Park, In-Chul Jung, Won Kyung Lee, Young Sun Lee, Hyoung Kook Park, Hyo Jin Go, Kiseong Kim, Nam Kyoo Lim, Jin Tae Hong, Sun Yung Ly, and Seok Seon Rho

 

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The Effects of l-theanine on Alpha-Band Oscillatory Brain Activity During a Visuo-Spatial Attention Task

Author: Manuel Gomez-Ramirez and Simon P. Kelly and Jennifer L. Montesi and John J. Foxe

Background/Objectives Ingestion of the non-proteinic amino acid l-theanine (γ-glutamylethylamide) has been shown to influence oscillatory brain activity in the alpha band (8–14 Hz) in humans during resting electroencephalographic (EEG) recordings and also during cognitive task performance. We have previously shown that ingestion of a 250-mg dose of l-theanine significantly reduced tonic (background) alpha power during a demanding intersensory (auditory-visual) attentional cueing task. Further, cue-related phasic changes in alpha power, indexing the shorter-term anticipatory biasing of attention between modalities, were stronger on l-theanine compared to placebo. This form of cue-contingent phasic alpha activity is also known to index attentional biasing within visual space. Specifically, when a relevant location is pre-cued, anticipatory alpha power increases contralateral to the location to be ignored. Here we investigate whether the effects of l-theanine on tonic and phasic alpha activity, found previously during intersensory attentional deployment, occur also during a visuospatial task. Subjects/Methods 168-channel EEG data were recorded from thirteen neurologically normal individuals while engaged in a highly demanding visuo-spatial attention task. Participants underwent testing on two separate days, ingesting either a 250-mg colorless and tasteless solution of l-theanine mixed with water, or a water-based solution placebo on each day in counterbalanced order. We compared the alpha-band activity when subjects ingested l-Theanine vs. Placebo. Results We found a significant reduction in tonic alpha for the l-theanine treatment compared to placebo, which was accompanied by a shift in scalp topography, indicative of treatment-related changes in the neural generators of oscillatory alpha activity. However, l-theanine did not measurably affect cue-related anticipatory alpha effects. Conclusions This pattern of results implies that l-theanine plays a more general role in attentional processing, facilitating longer-lasting processes responsible for sustaining attention across the timeframe of a difficult task, rather than affecting specific moment-to-moment phasic deployment processes.

 

 

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The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans

Author: Lu K and Gray MA and Oliver C and Liley DT and Harrison BJ and Bartholomeusz CF and Phan KL and Nathan PJ

L-Theanine (δ-glutamylethylamide) is one of the predominant amino acids ordinarily found in green tea, and historically has been used as a relaxing agent. The current study examined the acute effects of L-theanine in comparison with a standard benzodiazepine anxiolytic, alprazolam and placebo on behavioural measures of anxiety in healthy human subjects using the model of anticipatory anxiety (AA). Sixteen healthy volunteers received alprazolam (1 mg), L-theanine (200 mg) or placebo in a double-blind placebo-controlled repeated measures design. The acute effects of alprazolam and L-theanine were assessed under a relaxed and experimentally induced anxiety condition. Subjective self-reports of anxiety including BAI, VAMS, STAI state anxiety, were obtained during both task conditions at pre- and post-drug administrations. The results showed some evidence for relaxing effects of L-theanine during the baseline condition on the tranquil–troubled subscale of the VAMS. Alprazolam did not exert any anxiolytic effects in comparison with the placebo on any of the measures during the relaxed state. Neither L-theanine nor alprazalam had any significant anxiolytic effects during the experimentally induced anxiety state. The findings suggest that while L-theanine may have some relaxing effects under resting conditions, neither L-theanine not alprazolam demonstrate any acute anxiolytic effects under conditions of increased anxiety in the AA model.

 

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Author: Kenta Kimura and Makoto Ozeki and Lekh Raj Juneja and Hideki Ohira

L-Theanine is an amino acid contained in green tea leaves which is known to block the binding of l-glutamic acid to glutamate receptors in the brain. Because the characteristics of l-Theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in a laboratory setting using a mental arithmetic task as an acute stressor. Twelve participants underwent four separate trials: one in which they took l-Theanine at the start of an experimental procedure, one in which they took l-Theanine midway, and two control trials in which they either took a placebo or nothing. The experimental sessions were performed by double-blind, and the order of them was counterbalanced. The results showed that l-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition. Moreover, analyses of heart rate variability indicated that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. Thus, it was suggested that the oral intake of l-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.

 

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Author: Takashi Tachiki and Yukitaka Okada and Makoto Ozeki and Tsutomu Okubo and Lekh Raj Juneja and Nagahiro Yamazaki

It is intended to provide a novel process for efficiently producing theanine, thereby enabling convenient and industrially advantageous production of theanine. Pseudomonas citronellosis GEA, which has been newly isolated from soil in nature and selected, is a theanine-producing strain belonging to the species citronellosis of the genus Pseudomonas and showing a Ϝ-glutamyl transfer reaction. Theanine can be highly efficiently produced, compared with the existing methods, by using glutaminase originating in the above strain in a mixture of glutamine with ethylamine at pH 9 to 12.

 

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