The Protective Effect of Hydroalcoholic Extract of Green Tea (Camellia sinensis L.) on Anxiety Behaviors Induced with Chronic Noise Stress in Adult Male Wistar Rats

Background: The recruitment of medicinal herbs for the treatment of psychological disorders such as anxiety and stress has a long history. The purpose of the present study was to investigate the compensatory effects of hydroalcoholic extract of green tea on anxiety behaviors that are induced by noise stress in male Wistar rats. Methods: In this study, male Wistar rats weighing 200±20 g were randomly divided into six groups (n = 10): 1) control group, 2) sham- noise stress (two times per day and each time for 15 minutes, for 21 days, without noise stress), 3) chronic noise stress (two times per day and each time for 15 minutes, for 21 days, at 87.3 dB(A) and the frequency of 80 kHz), 4) Green tea (50, 100, 150 mg/kg i.p. for three weeks), 5) sham- green tea with saline injection for 21 days, 6) noise stress + green tea extract (50, 100, 150 mg/kg i.p. for three weeks). Their serum cortisol levels was measured by ELISA test before and after the tests. Behavioral tests were performed including elevated plus-maze, territory discrimination, and passive avoidance test. All statistical analyses were performed using SPSS software. Results: Serum corticosterone levels significantly decreased in noise stress groups treated with green tea compared to the control group (P<0.05). Based on the passive avoidance test, the time spent in the dark box showed a significant decrease in the noise stress group treated with green tea (150 mg/kg) compared to the noise stress group. Based on the territory discrimination test, the delay for entering the foreign segment in the green tea treated-groups showed a significant decrease (P<0.05) as compared to the noise stress group. The results of the elevated plus-maze test showed a significant increase in the time spent on the open arms in green tea extract-treated groups in comparison with noise stress group. Conclusion: Findings show the unique properties of green tea extracts in reducing serum corticosterone levels and improvement of anxiety behaviors caused by noise stress in animals. In addition, the useful effects of herbal medicine on anxiety disorders were confirmed in our study.