[Antidepressant effects of the extract of Dendrobium nobile Lindl on chronic unpredictable mild stress-induced depressive mice].

To investigate whether the extract of Dendrobium nobile Lindl (DNL) has an antidepressant effect on chronic unpredictable mild stress (CUMS)-induced depressive mice, 72 BALB/c male mice were randomly divided into the control group, the CUMS model group, the extract of DNL groups (50, 100 and 200 mg/kg DNL, i.g.) and the paroxetine group (10 mg/kg, i.g.). The different doses of DNL or the paroxetine was administered orally once daily to CUMS mice for 8 weeks (containing two-week preventive medication before the modeling). The same volume of distilled water was given to the control group and the CUMS group. Except for the control group, the other mice were exposed to chronic stress for 35 days. Behavioral tests were performed by using the sucrose preference test (SPT), the novelty-suppressed feeding (NSF) test, the tail suspension test (TST), and the forced swim test (FST). The levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) were measured by the liquid chromatography-mass spectrometer (LC-MS)/MS. Compared with the control group, obvious behavioral changes were observed in the CUMS group after 5-week CUMS, including a decrease in the sucrose consumption, an increase in the latency to feeding in the NSF test and a prolongation of the immobility time in the TST. Compared with the CUMS group, the application of DNL resulted in a dose-dependent increase in sucrose consumption (P < 0.01) as paroxetine (10 mg/kg) did and a significant dose-dependent decrease in the latency to feeding in the NSF test (P < 0.05). In the TST, the application of paroxetine (10 mg/kg) and the high-dose DNL (200 mg/kg) obviously decreased the immobility time when compared with the CUMS group (P < 0.05). In the FST, compared with the CUMS group, all the groups had no significant differences in the immobility time (P > 0.05). In addition, in the hippocampus and cortex, the levels of 5-HT and DA were significantly decreased in the CUMS group compared with the control group (P < 0.05). In comparison with the CUMS group, paroxetine obviously increased the DA levels in the hippocampus and the cortex and the 5-HT level in the hippocampus (P < 0.05). DNL (50 and 200 mg/kg) significantly increased the DA level in cerebral cortex of the brain, and DNL (100 and 200 mg/kg) increased the DA level in the hippocampus. The 5-HT level in the 200 mg/kg DNL group was notably increased in both two brain regions (P < 0.05), but the 5-HT level in the 100 mg/kg DNL group was significantly increased only in the hippocampus (P < 0.01). These findings indicate that the extract of DNL has an antidepressant-like effect on CUMS-induced depressive mice and its mechanism may be related to the changes in DA and 5-HT in the hippocampus and cortex.