Facilitated Neurogenesis in the Developing Hippocampus After Intake of Theanine, an Amino Acid in Tea Leaves, and Object Recognition Memory
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Theanine, γ-glutamylethylamide, is one of the major amino acid components in green tea. In this study, cognitive function and the related mechanism were examined in theanine-administered young rats. Newborn rats were fed theanine through dams, which were fed water containing 0.3% theanine, and then fed water containing 0.3% theanine after weaning. Theanine level in the brain was under the detectable limit 6 weeks after the start of theanine administration. Theanine administration did not influence locomotor activity in the open-field test. However, rearing behavior was significantly increased in theanine-administered rats, suggesting that exploratory activity is increased by theanine intake. Furthermore, object recognition memory was enhanced in theanine-administered rats. The increase in exploratory activity in the open-field test seems to be associated with the enhanced object recognition memory after theanine administration. On the other hand, long-term potentiation (LTP) induction at the perforant path-granule cell synapse was not changed by theanine administration. To check hippocampal neurogenesis, BrdU was injected into rats 3 weeks after the start of theanine administration, and brain-derived neurotropic factor (BDNF) level was significantly increased at this time. Theanine intake significantly increased the number of BrdU-, Ki67-, and DCX-labeled cells in the granule cell layer 6 weeks after the start of theanine administration. This study indicates that 0.3% theanine administration facilitates neurogenesis in the developing hippocampus followed by enhanced recognition memory. Theanine intake may be of benefit to the postnatal development of hippocampal function.
KeywordsTheanine Green tea Neurogenesis Memory LTP BDNF Hippocampus
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