Dopamine antinociceptive system

The article presents modern views on structure and functioning of dopaminergic structures of the brain and spinal cord and their role in mechanisms of antinociception, formation, and chronification of different pain syndrome types. The paper provides a detailed description of analgesic effects of various dopamine receptors in the structures of the CNS (the spinal cord, ventral tegmental area, periaqueductal gray, corpus striatum, nucleus accumbens, hypothalamus, and medial prefrontal cortex) which function as the dopaminergic antinociceptive system. The results of numerous investigations carried out on models of neuropathic pain syndrome have shown that D2 dopamine receptors possess the greatest analgesic activity. Their antinociceptive mechanism of action is effectuated at the level of substantia gelatinosa of the spinal cord and cerebral dopaminergic structures. D1‑like receptors have lower analgesic activity and different mechanisms of action depending on localization within the brain. High availability of D2/D3 receptors in corpus striatum is indicative of a low synaptic level of endogenous dopamine and leads to reduction of pain perception threshold. On the contrary, low availability of D2/D3 receptors results in the increase of pain perception threshold. The dopaminergic antinociceptive system is characterized by a modulating effect on other neurotransmitter systems participating in nociception and antinociception. An important mechanism of antinociception of dopaminergic structures is connected with superadditivity and synergism of D2 receptors with opioid receptors. Proven participation of dopaminergic structures in pain perception and analgesia demonstrates a potential possible application of D2‑receptors agonists as an adjuvant method for achieving a greater effect in therapeutic multimodal schemes of analgesia.