Neural mechanisms of cutaneous nociceptive pain

Acute mechanical, thermal, and chemically induced pains in the skin are sig nalled by a set of specific nociceptive afferents, which encode the magnitu de of the perceived pain by their discharge intensity. After tissue injury or inflammation, a number of changes in the properties of the primary affer ent occur parallel to profound changes in the central nervous system. Prima ry hyperalgesia (within the area of tissue injury) is best explained by cha nges of the properties of primary nociceptive afferents, whereas secondary hyperalgesia (increased pain sensitivity outside the area of tissue injury) critically requires functional changes in the central nervous system. Coll ectively, these changes are the basis for the many forms of hyperalgesia th at can present clinically as incident pain. Knowledge of the various types of hyperalgesia and their underlying mechanisms is required for better trea tment of this challenging aspect of chronic pain.