Melatonin (MT) plays an important role in the regulation of physiological and neuroendocrine functions, such as control of circadian rhythms and synchronization of seasonal reproductive rhythms in mammals. Melatonin shows its antinocieeptive effects in a dose - dependent manner. Melatonin is influencing the mechanical allodynia but not thermal hyperalogia. Antinociceptive effects of melatonin are having the significant connection with the MT2 receptor stimulation and activation of the opioid system.