Modulation of Anxiolytic-Like and Antidepressant-Like Effects of Melatonin by Imipramine in Wistar Rats: Possible Interaction with Central Monoaminergic Systems

Our current study aims to explore the interaction of melatonin (MEL) with the monoaminergic system on the pathophysiology of affective disorders in Wistar rats. We mention here that, the role of monoaminergic transmission in the pathophysiology of affective disorders in humans is demonstrated in most recent reports. In this sense, our current work aims to explore the effect of melatonin (MEL) with or without imipramine (IMP) on levels of depression and anxiety in Wistar rats and would determine the role of MEL in modulating serotonin, noradrenaline and dopamine neurotransmission. From this point, twenty-four female Wister rats were divided into 4 groups of 6 animals and received subcutaneously during 4 weeks different doses of MEL (4 mg/kg), IMP (2 mg/kg) or MEL (4 mg/kg) + IMP (2 mg/kg). Behavioral performance especially anxiety and depression is measured in the open field (OFT), elevated plus maze (EPM) and forced swim test (FST). The anxiety-like and antidepressant-like effects were observed with MEL at 4 mg/Kg and IMP at 2 mg/Kg but the potentiating effect was more observed with the two combined molecules (MEL and IMP), since locomotors activity assessed by the OFT and EPM was not affected. These effects suggest that psychopharmacological actions of MEL are due, at least in part, to its ability to potentiate the central monoaminergic transmitter effects.