Mechanisms of Electroacupuncture-Induced Analgesia on Neuropathic Pain in Animal Model
Figure 1
Schematic diagram of EA-induced analgesia in neuropathic pain in the CNS. The peripheral injury information is first transmitted to substantia gelatinosa (SG) cells by primary afferent fibers. EA stimulation is carried up from marginal (M) cells tract to the brain via spinothalamic tract, where the signal is transmitted to the cortex and becomes conscious and also to intrinsic dorsal neurons where it involves cholinergic, ENKergic, and GABAergic neurons. The PAG in the midbrain projects down to the NRM in the middle of the medulla oblongata, and this in turn sends 5-HT fibers to the dorsal horn. LC sends NE fibers to the dorsal horn. NE, via -adrenoreceptors, enhances the spinal cholinergic and GABAergic neurons, involves a reduction in the release of pronociceptive transmitters in the primary afferents fibers, and inhibits the transmission of pain signals to the supraspinal level in the secondary afferents fibers. Serotonin activates enkephalin (ENK) and GABA intrinsic neurons through 5-HT3 serotonergic receptors and inhibits secondary afferents fibers via 5-HT1A serotonergic receptors. Cholinergic, ENKergic, GABAergic neurons, through its M1 muscarinic receptors, , opioid receptors, and GABAA and GABAB receptors control nociceptive inputs from the periphery to higher areas in the CNS. Abbreviations are as follows: SG: substantia gelatinosa; M: marginal cells; PAG: periaqueductal grey; NRM: nucleus raphe magnus; LC: locus coeruleus; 5-HT: serotonin; NE: noradrenalin; Ach: acetylcholine; and ENK: enkephalin.
