Evaluation of Antidepressant-like Effect of Morus Mesozygia Extract in Mice: the Monoaminergic Involvement

Morus mesozygia is a deciduous tree found in Nigeria and native to tropical Africa. This study was carried out to investigate the antidepressant-like effect of ethanol extract of Morus mesozygia (EEMM) leaves in Mice. The acute toxicity of EEMM was determined and the motor activity was assessed using the open field. The antidepressant activity of EEMM (2.5, 5, 10 mg/kg, i.p.) was investigated using forced swimming test (FST) and tail suspension test (TST). The possible mechanisms for antidepressant action were assessed with reserpine (2.5mg/kg) induced depression tests and antagonist pretreatment using parachlorophenylalanine (p-CPA 100 mg/kg, an inhibitor of serotonin synthesis), Ciproheptadine (3 mg/kg, a serotonin 5-HT2 receptor antagonist), Metergoline (4 mg/kg, a non-selective serotonin receptor antagonist), Prazosin (62.5 μg/kg, a α1 adrenoceptor antagonist), Yohimbine (1 mg/kg, α2-adrenoceptor antagonist), Propranolol (5mg/kg, a β adrenoceptor antagonist), Haloperidol (0.2mg/kg, a non-selective dopamine receptor antagonist), or Sulpiride (50 mg/kg, a dopamine D2 receptor antagonist). The results showed, the median lethal dose (LD50) of Morus mesozygia was 2449 mg/kg, a significant dose dependent reduction in immobility time in FST and TST. It was also found that EEMM significantly antagonized hypothermia, ptosis and diarrhea induced by reserpine. The antidepressant-like activity in FST was blocked by pretreatment with p-CPA, Prazosin, Propranolol, Haloperidol and Sulpiride, whereas, pretreatment with Cyproheptadine markedly reduced the immobility time of mice in FST. In Conclusion, the results of this investigation provide evidence that confirm the significant antidepressant-like activity of EEMM in mice and it involves the monoaminergic system which is probably mediated through reuptake inhibition.