Objective  To explore the effect and mechanism of tenuifolin (TEN) on mental behavior in depression model mice.

  Methods  Totally 72 specific pathogen free Kuming mice were randomly divided into 6 groups (12 in each group): a control and a model group treated with saline gavage, a positive control group with 3.5 mg/kg fluoxertine hydrochloride, and three TEN groups administered with TEN by gavage at doses of 3, 6, 9 mg/kg per day continuously for 4 weeks. The mouse depression model was established with chronic unpredictable mild stress and 28-day isolation method. At the end of the treatments, fixed time forced swimming and tail suspension test were performed for all the mice and then brain tissue samples of the mice were collected for measurements of 5-hydroxytryptamine (5-HT) content and the activity of indoleamine 2, 3-dioxygenase (IDO) in cerebral cortex and the activity of acetylcholinesterase (AchE) and choline acetyl-transferase (ChAT) in hippocampus.

  Results  Compared with those for the control mice, the fixed time of forced swimming test (215.16 ± 18.39 s) and tail suspension test (182.89 ± 14.90 s) were obviously prolonged the for the model mice (both P < 0.01). Compared with those for the model mice, the fixed time of forced swimming test (183.64 ± 14.92 s) and tail suspension test (156.09 ± 12.38 s) were shortened obviously for the mice treated with 9 mg/kg TEN (both P < 0.05). Lower content of 5-HT (28.96 ± 2.50 μg/L) but higher activity of IDO (11.87 ± 1.11 ng/mg) in cerebral cortex were detected in the model mice in comparison with those in the control mice (both P < 0.01). Significantly increased 5-HT content (36.41 ± 3.32 μg/L) and declined IDO activity (7.24 ± 0.71 ng/mg) in cerebral cortex were detected in the mice treated with 9 mg/kg TEN compared to those in the model mice (both P < 0.05). In comparison with those of the control mice, the AchE activity (1.149 ± 0.218 U/mg) increased but the ChAT activity (50.44 ± 4.43 U/g) declined significantly in hippocampus of the model mice (both P < 0.01). Significantly increased AchE activity (0.584 ± 0.147 U/mg) and decreased ChAT activity (86.05 ± 3.94 U/g) in hippocampus were detected in the mice treated with 9 mg/kg TEN compared to the model mice (both P < 0.05).

  Conclusion  To some extent, TEN can improve mental behavior in depression model mice; the mechanism may be related to the increased expression of 5-HT and decreased expression of IDO in cerebral cortex and the decreased activity of AchE and the increased activity of ChAT activity in hippocampal neurons of the mice.