A Survey of Systems Involved in Nociceptive Processing

High-intensity afferent input, tissue injury and inflammation, and injury to the peripheral nerve will initiate pain states with characteristic psychophysical properties. As will be considered below, this information processing can be modified to change the content of the message generated by a given stimulus to enhance the pain state (e.g., produce hyperalgesia), normalize a hyperalgesic state, or produce a decrease in pain sensitivity (e.g., produce analgesia). Management of that pain state is addressed by the use of agents or interventions which though specific targets at the level of the sensory afferent, the spinal dorsal horn or at higher-order levels (supraspinal) modify the contents of the sensory message generated by that physical stimulus. The important advances in the development of pain therapeutics have reflected upon the role played by specific underlying mechanisms which regulate these events.