OBJECTIVETo study the effects of theanine on dopamine (DA), 5-hydroxy tryptamine (5-TH) and glutamate receptor 2 (GluR2) mRNA, phospholipase-γ1 (PLC-γ1) mRNA in cerebral ischemia-reperfusion injury rats and explore the mechanism of protective effects of theanine on the induced brain injury by ischemia-reperfusion in rats.

METHODSAccording to random number table, a total of 56 sprague-dawley rats in SPF grade about six-week old and 100 - 120 grams weighting were divided into five groups according to the body weight levels: model group (n = 12), sham-operation group (n = 8), low theanine group (10 mg/kg), middle theanine group (30 mg/kg) and high theanine group (90 mg/kg). There were 12 rats in each of the theanine group. The rats in model group and sham-operation groups were given distilled water, and the rats in theanine groups were given corresponding theanine solution intragastrically for fifteen days. Then the cerebral ischemia-reperfusion injury was established by middle cerebral artery occlusion (MCAO). The score of neurological behavior was evaluated at the 3rd and 24th hours after reperfusion. Rats were sacrificed at 24 hours after reperfusion, the concentrations of DA, 5-HT and theanine in rats brain following ischemia-reperfusion were determined. At the same time, we determined the levels of reactive oxygen species (ROS) and activities of catalase (CAT) in mitochondria of brain. The expressions of GluR2 mRNA and PLC-γ1 mRNA in rat brain were examined by reverse transcription polymerase chain reaction (RT-PCR) technique.

RESULTSThe score of neurological behavior of rats in model group, theanine-low, middle, high dose groups at the 3rd hour was 6.000 ± 0.926, 4.100 ± 0.738, 3.444 ± 0.726 and 2.250 ± 0.886 respectively (F = 29.70, P < 0.01), and the score at the 24th hour in these groups was 6.625 ± 0.916, 5.000 ± 0.817, 3.667 ± 0.707 and 2.625 ± 0.916 respectively(F = 34.68, P < 0.01). The concentration of DA in model group, theanine-low, middle, high dose groups and sham-operation group was (10.26 ± 1.12), (12.48 ± 1.09), (14.55 ± 0.94), (15.97 ± 0.92) and (11.98 ± 0.63) µg/g respectively (F = 43.76, P < 0.01). The concentration of 5-HT in these groups was (1.091 ± 0.160), (0.818 ± 0.101), (0.571 ± 0.050), (0.453 ± 0.111) and (0.863 ± 0.063) µg/g respectively (F = 48.68, P < 0.01). The level of ROS was (3.072 ± 0.503), (1.331 ± 0.268), (1.295 ± 0.061), (0.804 ± 0.200) and (2.158 ± 0.218) U×min⁻¹×mg⁻¹ (F = 80.82, P < 0.01) respectively and the activities of CAT in these groups were (4.880 ± 1.121), (8.405 ± 1.356), (9.535 ± 2.511), (15.090 ± 4.054) and (21.260 ± 6.054) U/g respectively (F = 28.58, P < 0.01). The expressions of GluR2 mRNA were 0.842 ± 0.020, 1.063 ± 0.100, 1.170 ± 0.152, 1.254 ± 0.131 and 1.012 ± 0.056 respectively (F = 9.23, P < 0.01). The expressions of PLC-γ1 mRNA in these groups were 0.737 ± 0.090, 0.887 ± 0.045, 0.963 ± 0.025, 0.991 ± 0.049 and 0.867 ± 0.079 respectively(F = 10.24, P < 0.01).

CONCLUSIONTheanine has a protective effect on the induced brain injury by ischemia-reperfusion in rats, which might be associated with its interaction with monoamine neurotransmitters and up-regulating the expressions of GluR2 mRNA and PLC-γ1 mRNA.