The role of glia in the spinal cord in neuropathic and inflammatory pain.

Chronic pain, both inflammatory and neuropathic, is a debilitating condition in which the pain experience persists after the painful stimulus has resolved. The efficacy of current treatment strategies using opioids, NSAIDS and anticonvulsants is limited by the extensive side effects observed in patients, underlining the necessity for novel therapeutic targets. Preclinical models of chronic pain have recently provided evidence for a critical role played by glial cells in the mechanisms underlying the chronicity of pain, both at the site of damage in the periphery and in the dorsal horn of the spinal cord. Here microglia and astrocytes respond to the increased input from the periphery and change morphology, increase in number and release pro-nociceptive mediators such as ATP, cytokines and chemokines. These gliotransmitters can sensitise neurons by activation of their cognate receptors thereby contributing to central sensitization which is fundamental for the generation of allodynia, hyperalgesia and spontaneous pain.