Monoaminergic Neurotransmission on the Antidepressant Effect of Leaf and Root Extracts of Rauwolfia vomitoria on the Locomotion and Immobility of Sprague‐Dawley Rats

Rauwolfia vomitoria is one of the medicinal plants which is used traditionally to manage hypertension, diabetes and mental disorder. This study is to investigate antidepressant-like effect of the leaf and root aqueous and ethanol extracts of R. vomitoria in the rat model using neurobehavioural indices; open field test and forced swimming test. The effect of the plant extracts on monoamine neurotransmiters’ system was also investigated. The neurobehavioural response of rats by open field test and forced swim test showed that there was a reduction in the explorative tendencies of the rats administered the aqueous and ethanol root extracts (0, 100, 200, 300, 400, 500mg/kg) compared to the control, while forced swim test reduced the immobility time of rats across all treatment groups, except 500mg/kg group. Neurotransmitter levels (serotonin, dopamine and norepinephrine) in plasma and brain of rats administered the different concentrations of root extracts exhibited significant (p <0.05) increase.The reduction in monoamine oxidase activity by the standard drugs and R. vomitoria extracts confirm that the mechanism of action R. vomitoria root extracts could be through inhibition of monoamine oxidase activity. Therefore, the mode of action may be due in part to the increase in monoamine levels or by suppression of the reuptake of the monoamine neurotransmiters. This study established that R. vomitoria root extract has antidepressant-like effect in rats.