Table 4.

Summary of Mechanisms for SCS, TENS, and MA

Type of treatment	Mechanism
SCS	Utilizes several neurotransmitters and their receptors including serotonin, opioids, GABA and acetylcholine, inhibits release of glutamate and aspartate, and reduces glial cell activation.
TENS	Activates δ-opioid receptors, PAG, RVM, spinal inhibitory pathways, GABA, and reduces dorsal horn sensitization, glutamate, and substance P release.
MA	Activates descendent inhibitory pathways, releases ATP peripherally, alters inflammation and immune cell phenotype.

SCS: spinal cord stimulation, TENS: transcutaneous electrical nerve stimulation, MA: manual acupuncture, GABA: gamma-aminobutyric acid, PAG: periaqueductal gray, RVM: rostral ventromedial medulla, ATP: adenosine triphosphate.