Background This study aimed to investigate the regulatory effects of L-theanine on secretion of immune cytokines, hormones, and neurotransmitters, and mRNA expression of phospholipase C (PLC) in rats, and to explore its regulatory mechanism in immune function. 5-hydroxytryptamine in the pituitary and hippocampus, resulting in decrease in corticosterone level in the serum. L-theanine administration decreased the mRNA expressions of PLC isomers in the liver GSK429286A and PLC-1 and PLC-1 in the spleen. Interestingly, mRNA expressions of PLC-f1 in the spleen and PLC isomers mRNA in the heart were up-regulated by L-theanine administration. Conclusions Administration of 400 mg/kg BWL-theanine improved immune function of the rats by increasing the splenic weight, altering the Th2/Th1 cytokine balance, decreasing the corticosterone level in the serum, elevating dopamine and 5-hydroxytryptamine in the brain, and regulating the mRNA expression of PLC isomers in the heart. [1]. L-theanine is an important bioactive component of tea, and has many physiological functions, such as regulating immune response [2,3], preventing diseases [4], anti-tumor [5], relaxing neural tension [6], and anti-oxidation stress [7]. Previous studies have shown that L-theanine can enhance innate immune function by regulating the secretion of immune cytokines. Bukowski et al. [8] demonstrated GSK429286A that ingestion of L-theanine by drinking tea induces innate immune response and immunologic memory in humans. The explanation is that L-theanine can be degraded by glutaminase to glutamate and ethylamine [9], and the latter, as a non-peptide alkylamine antigen, can be subsequently identified by the gamma delta T cells ( T cells) in peripheral bloodstream, as well as the primed T cells further take part in a memory space response [3]. Such priming leads to a non-memory response to entire bacterias and lipopolysaccharide also, which is seen as a interleukin-12 (IL-12)-reliant secretion of interferon- (IFN-) by T cells and their proliferation [2]. Further medical studies [8] possess found that dental administration of L-theanine enhances the experience of T cells, promotes the secretion of IFN-, and additional inhibits tumor activity. The feasible mechanism could possibly be that L-theanine metabolite-ethylamine induces the prenyl pyrophosphate build up GSK429286A by inhibiting the mevalonate pathway, and promotes the proliferation of T cells [3] then. Wen et al. [10] proven that adding 400 mg L-theanine/kg daily in the dietary plan increases the degree of secretory IgA in the jejunum as well as the degrees of IL-2 and IFN- in the serum of baby hens. Hwang et al. [11] suggested that treatment of -glucan (400 mg/kg give food to) plus L-theanine (80 mg/kg give food to) in weaning piglets lessens the inflammatory reactions against Gram-negative infection via the inhibition of pro-inflammatory cytokines (e.g., IFN- and TNF-f) hyperproduction and improvement of anti-inflammatory cytokine (IL-10) creation after lipopolysaccharide publicity, inside a time-dependent way. Kurihara et al. [7] reported that dental administration of L-theanine and L-cysteine can boost IgG GSK429286A level in the bloodstream of mice. Takagi et al. [12] demonstrated out that mixed administration of L-theanine and L-cystine before major immunization enhances the serum antigen-specific IgM and IgG amounts in 24-month-old mice, decreases the lung viral titers at day time 6, and escalates the anti-influenza-virus IgG antibody at day time 10 after influenza disease disease in 13-month-old mice, which the serum IL-10/IFN- percentage is raised in the spleens of mice. After becoming consumed in to the physical body, L-theanine can penetrate the blood-brain hurdle and regulate the secretion of neurotransmitters of central anxious program cells [13] and degrees of hormones such as for example corticosterone (CORT) and adrenaline (EPI) in the serum. Peng et al. [14] proven that L-theanine can boost degrees of 5-hydroxytryptamine (5-HT) and noradrenaline, and lower degrees of adrenocorticotropic CORT and hormone in the hippocampus and prefrontal cortex of rats. Yamada et al. [15] discovered that L-theanine shot in to the rat mind striatum escalates the focus of glycine and dopamine (DA) in the perfusate by ENG activating -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acidity receptors. Another scholarly research [16] shows that whenever mom rats are given L-theanine advertisement libitum, the concentrations of DA, 5-HT, -amino and glycine butyric acidity are improved in the 3-week-old baby rat mind, as well as the mRNA degree of nerve growth element is improved in.