Anxiolytic-like Effects of Noni juice (Morinda citrifolia L.) on the Respective Changes of Neurotransmitters in Rat Brain in the Elevated Plus-maze Test

Noni (Morinda citrifolia L.) has long been used to treat various conditions in folklore medicine. Presently, most studies focus on antioxidant and anti-cancer activities while it is also claimed by noni juice-consumers to produce happiness. Mood disorders, e.g. anxiety, are symptoms that reflected the disorder of neurotransmitters, one of the most prominent is the monoaminergic system. Anxiety affects people throughout the world; people have been seeking medicine for treatment while natural products may also alleviate this unfavorable symptom. The present study examined whether noni contained anxiolytic-like effect when tested with elevated plus-maze (EPM), a standard test for anxiety, and whether this effect was related to change in monoamine transmitters in brain. Male Wistar rats were fed either noni juice or water (1 ml/day, PO for 1.5 days), and the anxiety level was measured with EPM. The brain monoamines were then analyzed with HPLC-electrochemical detector. We found that the noni-treated rats spent more time in the opened-arm than the control rats, indicating that the noni-treated rats were less anxious than the control rats. The neurochemical analysis revealed significant changes in noradrenergic, dopaminergic or serotonergic systems in amygdala, hippocampus and substantia nigra of the noni-treated group. These findings indicated that the noni juice produced anxiolytic-like behaviors in rats partially by modulating neurochemical metabolisms in brain regions related to anxiety.