Protective effects of green tea polyphenols on cognitive impairments induced by psychological stress in rats

This study was conducted to explore the modulation of GTPs on cognitive performances in psychological stress rats. Wistar rats were randomly assigned to five groups as follows: control group, stress group, and three stress groups with low, medium and high-doses of GTPs modulation respectively. The changes of cognitive performances were examined by open-field test, water maze and step-through test. Results demonstrated that serum levels of cortisol were all increased obviously in four stress groups. The cognitive performances of stress group were changed evidently. And these changes were improved in stress medium and high-doses of GTPs modulation groups. In addition, plasma levels of IL-6 and IL-2 were increased in four stress groups, serum norepinephrine and dopamine were decreased dramatically in stress group and stress low-dose GTPs modulation group. The serum norepinephrine and dopamine levels in stress medium and high-doses of GTPs modulation groups were increased in contrast to that of stress group. Furthermore, the changes of anti-oxidative capacity in brain tissue were also measured. Except superoxide dismutase, the changes of malondialdehyde, reactive oxidative species and total anti-oxidative capacity of stress group were significantly different from that of control group. These changes in stress medium and high-doses of GTPs modulation groups were improved. Our results suggested that psychological stress impaired body's cognitive performances, and moderate GTPs modulation could improve these abnormal changes. To our knowledge, this is the first report showing the improving effects of GTPs on cognitive dysfunctions induced by psychological stress. (c) 2009 Elsevier B.V. All rights reserved.