Role of 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. The scientific evidence to suggest its medicinal use especially in mental health treatment is lacking. This study aimed to investigate the antidepressant-like effect of the leaf and root extracts of R. vomitoria in the rat model using neurobehavioural indices; open field test and forced swimming test. Subsequently, the effect of the extracts on monoamine neurotransmitters system was investigated. The neurobehavioral 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 (125, 250, 500 mg/kg) compared to the control while forced swim test reduced the immobility time of rats across all treatment groups except 500 mg/kg group. Neurotransmitter levels (serotonin, dopamine and norepinephrine) in plasma and brain of rats administered the different concentration of root extracts exhibited significant (p<0.05) increase. Thus, the mode of action may be due in part to the increase in monoamine levels or by suppression of the reuptake of the monoamine neurotransmitters. This study established that R. vomitoria root extract has antidepressant-like effect in rats.