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Abstract
The purpose of this study is to investigate whether the combination of green tea extract (GTE) and L-theanine has an anxiolytic effect by oral administration through behavioral tests and neurtransmitters (or hormone) anaylses. Four week oral administration of GTE (24 mg/kg), L-theanine (4 mg/kg) or their combination showed anxiety-reducing effects determined by increasing numbers of head-dips in a hole board test and reducing retention time in a rota-rod test without changing spontaneous locomotor activity. Biochemical analyses indicated that the test materials decreased dopamine (DA), noradrenaline (NA), corticosterone (CS) and increased serotonin (5-HT) levels in brain cortex, hippocampus, and striatum, which suggests a possible mechanism of previous behavioral tests. Although the synergistic effects of GTE and L-theanine combination were not observed on the behavioral test, its effects on neurotransmitters (NA, CS) were synergistic and comparable to diazepam (2 mg/kg i.p.) with much less muscle relaxation side effect. Therefore, a combination of GTE and L-theanine may be useful as a functional food ingredient having an anxiolytic effect.
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Figure 1.
Green tea extract (GTE) and L-theanine combination shows anxiolytic activity by increasing number of head dips in hole board test. Diazepam (DZP) was administered intraperitoneally 30 mins before test. The results are represented as mean±SE. ∗∗P<0.01 compared with non-treated control.
Figure 2.
Green tea extract (GTE) and L-theanine combination shows muscle relaxant activity by rota rod test. Diazepam (DZP) was administered intraperitoneally 30 mins before test. The results are represented as mean±SE. ∗∗P<0.001 compared with nontreated control.
Figure 3.
Green tea extract (GTE) and L-theanine combination shows no effect on spontaneous locomotor activity. Diazepam (DZP) was administered intraperitoneally 30 mins before test. The results are represented as mean±SE.
Figure 4.
Green tea extract (GTE) and L-theanine combination shows anxiolytic activity by modulating neurotransmitters. Diazepam (DZP) was administered intraperitoneally 30 mins before test. (a) dopamine (DA), (b) noradrenaline (NA), (c) serotonin (5-HT), (d) corticosterone (CS) concentrations in various brain areas (cortex, hippocampus and striatum). The results are represented as mean±SE. ∗∗ P<0.01.
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