Anxiolytic activity of aqueous extract of Camellia sinensis in rats

Objectives: The present study was undertaken to evaluate anxiolytic effect of Camellia sinensis (CS) and possible mechanism on acute and chronic administration in rats. Materials and Methods: Eight groups of rats with six in each group were used. Group I served as control. Group II received diazepam (1 mg/kg). Groups III, IV, and V received CS in doses of 3.3, 16.5, and 33 mg/kg, respectively. Three pharmacologically validated experimental models - elevated plus maze (EPM), light and dark box (LDB), and open field tests (OFT) - were employed. Each animal was tested initially in the EPM and then in the LDB, followed by the OFT in a single setting. In EMP, number of entries into, time spent in, and number of rears in each arm in a 5-min period were noted. In LDB, number of entries and time spent in bright arena, number of rears, and duration of immobility were noted. In OFT, number of peripheral and central squares crossed, time spent, and number of rears in central squares were observed for a 5-min period. One-way ANOVA followed by post hoc least significant difference test was performed. Results: In EPM and LDB, CS at 3.3, 16.5, and 33 mg/kg (acute and chronic models) increased the number of entries and time spent and rearing in the open arms and bright arena, respectively, compared to control. In the OFT, CS at 16.5 and 33 mg/kg significantly increased the number of squares crossed, time spent, and the number of rears in the central squares compared to control. Anxiolytic effect was dose dependent in EPM and LDB and CS at 33 mg/kg showed better anxiolytic activity compared to diazepam (1 mg/kg) in all models. Flumazenil (0.5 mg/kg) and bicuculline (1 mg/kg) completely inhibited while picrotoxin (1 mg/kg) partially inhibited the anxiolytic effect of CS. Diazepam and CS at 33 mg/kg reduced the locomotor activity in rats. Conclusion: CS has dose-dependent anxiolytic activity which is comparable to diazepam. Anxiolytic action of CS is likely mediated through GABA_A-benzodiazepine receptor - Cl - channel complex - since flumazenil and bicuculline inhibited the anxiolytic effect.