This theme issue focuses on the molecular, biochemical, anatomical and functional aspects of chronic pain states. The first chapters illustrate the importance of both peripheral and spinal mechanisms and the contributions of glial function to chronic inflammatory pain. Further, the supraspinal/spinal modulation of sensory processing and possible alterations in this complex ascending/descending relay that may contribute to chronic pain states as well as the supraspinal/spinal plasticity in a central pain syndrome due to spinal cord injury are discussed. Finally, the publication presents new information on the potential mechanisms that underlie chronic pain due to sustained opioid exposure, and the possible relationship between such paradoxical pain states and the development of opioid tolerance. Neuroscientists will find this publication of special interest as it focuses on the basic mechanisms of sensory processing.
