Immune responses of microglia in the spinal cord: Contribution to pain states

The role of microglia and their contribution to the development and maintenance of pain states has emerged as an attractive field of study. Sensitization of central nociceptors and interneurons is thought to be responsible for the symptoms of chronic neuropathic pain states. Microglia interact with these neurons at the site of injury or disease as well as remotely. Microglia can be activated by phagocytosis or through the activation of a number of constitutively expressed cell surface molecules. Once activated, microglia participate in both innate and adaptive immune responses and remain active indefinitely. Activated microglia contribute to pain states through the production of pro-inflammatory cytokines, chemokines and extracellular proteases. Activated microglia also exhibit a modulated cell surface receptor and ion channel profile. The activation of several intracellular pathways in microglia has also been implicated in pain states. Attenuation of microglia activity is being presented as a viable therapeutic approach with regard to not only the reduction of pain symptoms but also in preventing the development of chronic pain states. (C) 2012 Elsevier Inc. All rights reserved.