Abstract: In stressful modern society, pain caused by physical and mental disorders is an increasing social health problem all over the world. Physical and mental activity depends on the state of various neurotransmitters in the central nervous system (CNS). Monoaminergic systems play important roles in regulating physiological functions including nociception. It is well known that in the CNS, there are descending pathways related to nociceptive processing known as the descending antinociceptive system (DAS). Noradrenalin and serotonin are major components of the DAS that form the locus coeruleus (LC)-spinal dorsal horn noradrenergic circuit and periaqueductal gray (PAG)-rostro ventricular medulla (RVM)-spinal dorsal horn serotonergic circuit (Jordan et al., 2008). Dopaminergic pathways also play roles in regulating nociceptive processing in the CNS.