Role for monoaminergic systems in the antidepressant-like effect of ethanol extracts from Hemerocallis citrina

Ethnopharmacological relevance

Hemerocallis citrina, a traditional herbal medicine, has been used for the improvement of emotions in Eastern-Asia countries.

Aim of the study

Herein, we explored the antidepressant-like effect and its monoaminergic mechanism of the ethanol extracts from Hemerocallis citrina (HCE).

Materials and methods

Effect of HCE (90, 180 and 360 mg/kg, p.o.) on the immobility time was assessed in the mouse forced swim test (FST) and tail suspension test (TST), and locomotor activity was evaluated in the open-field test (OFT). Additionally, the monoamine neurotransmitters serotonin (5-HT), noradrenaline (NA) and dopamine (DA) levels involved in the antidepressant-like effect of HCE were also measured in the mice brain regions of frontal cortex and hippocampus.

Results

HCE (90, 180 and 360 mg/kg, p.o.) administration significantly reduced the immobility time in both the FST and TST without accompanying changes in locomotor activity in the OFT. The pretreatment of mice with WAY 100635 (0.1 mg/kg, s.c., a 5-HT_1A receptor antagonist), cyproheptadine (3 mg/kg, i.p., a 5-HT₂ receptor antagonist), prazosin (62.5 μg/kg, i.p., an α₁-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an α₂-adrenoceptor antagonist), propranolol (5 mg/kg, i.p., a β-adrenoceptor antagonist) or sulpiride (50 mg/kg, i.p., a dopamine D₂ receptor antagonist), but not SCH23390 (0.05 mg/kg, s.c., a dopamine D₁ receptor antagonist) prevented the antidepressant-like effect of HCE (360 mg/kg, p.o.) in the TST. In addition, HCE enhanced 5-HT and NA levels in the frontal cortex and hippocampus as well as elevated DA levels in the frontal cortex.

Conclusion

The results indicate that the antidepressant-like effect of HCE is dependent on the serotonergic (5-HT_1A and 5-HT₂ receptors), noradrenergic (α₁-, α₂- and β-adrenoceptors) and dopaminergic (D₂ receptor) systems as well as the elevation of 5-HT, NA and DA levels in the mouse brain.