Evaluation of antidepressant activity of methanol extract of (A. Rich) Tiegh using acute inflammatory model of depression in Swiss albino mice

Abstract

Introduction Depression has been a global public health issue for a while now. This has prompted many researches to develop safer and more effective treatment of depressive illness. Cytokines are believed to alter neurochemical and neuroendocrine processes that have wide-ranging effects on physiology and behavior including depression. Tapinanthus globiferus has been reported to be used in the management of depression and many other neuro-psychiatric illnesses. Aim The aim of this study is to evaluate the antidepressant activity of the methanol extract of Tapinanthus globiferus in acute inflammatory model of depression in mice. Methods The phytochemicals present in methanol leaves extract of Tapinanthus globiferus were screened for using simple chemical tests. LD50 of the extract was determined using OECD method. Anti-depressant effect of the extract was evaluated using tail suspension test (TST) and forced swim test (FST), while open field test was used to validate the observed activity of the extract. The levels of inflammatory cytokines and BDNF were assayed using ELISA kits Results Saponins, cardiac glycosides, flavonoids, alkaloids, tannins, steroids and triterpenoids, while anthraquinones were absent in the extract. The median lethal dose (LD50) of the extract was greater than 5000 mg/kg. The extractsignificantly (p<0.05) reduced body temperature of the mice (measured rectally), and at the extract at highest dose, it significantly (p<0.05) reduced immobility time that was comparable to fluoxetine in TST. However, in FST, a significant (p<0.05) reduction in immobility was observed only in the fluoxetine group in comparison to the LPS-only group. Correspondingly, in this study, the mice in the LPS-only group had higher levels of pro-inflammatory cytokines; Interleukin-1 (IL-1) and Interleukin-6 (IL-6), and cortisol compared to extract treated groups while BDNF level was much higher in the extract treated group compared to the LPS-only and Normal saline group. Conclusion The methanol extract of Tapinanthus globiferus possesses antidepressant activity which may involve amelioration of inflammatory response and enhancement of neurotrophic factors in mice. This provides scientific basis for the use of the plant in the management of depression in traditional medicine.