| Abstract: | L‐theanine, originally found in green tea, elicits various physiological effects, such as promoting relaxation, improving concentration and learning ability, and providing antianxiety‐like and antidepressant‐like properties. This study aims to investigate the effects of L‐theanine (2 mg/kg) on monoamine levels in an animal model of depression. The effect of l ‐theanine on the symptoms of depression was examined through the open‐field test, sucrose preference test, and forced swim test. The monoamine neurotransmitters that involve serotonin (5‐HT), norepinephrine (NE), and dopamine (DA) were measured in the limbic–cortical–striatal–pallidal–thalamic (LCSPT)‐circuit related brain regions, including the prefrontal cortex (PFC), nucleus accumbens (NAC), striatum (ST), amygdala, and hippocampus (HIP). L‐theanine ameliorated the depressive‐like behaviors in the chronic unpredictable mild stress (CUMS) rat model. In the PFC, NAC, and HIP, L‐theanine administration significantly increased the levels of 5‐HT, NE, and DA. In the ST, the levels of 5‐HT and DA were increased after the administration of L‐theanine. However, in the HIP, only the level of DA significantly changed after the treatment of L‐theanine. Taken together, these results indicated that L‐theanine has possibly antidepressant‐like effects in the CUMS rat model, which could be mediated by the monoamine neurotransmitters in the LCSPT‐circuit related brain regions. |
