Open Peer Commentary Controversies in Neuroscience V: Persistent pain
Central sensitization following intradermal injection of capsaicin
William D. Willis Jr. a1 a1 Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston, TX 77555-1069
Intradermal capsaicin in humans causes pain, primary
hyperalgesia, and secondary mechanical hyperalgesia and allodynia.
Parallel changes occur in the responses of primate spinothalamic tract
cells and in rat behavior. Neurotransmitters that trigger secondary
mechanical hyperalgesia and allodynia include excitatory amino acids
and substance P. Secondary mechanical allodynia is actively maintained
by central mechanisms. Our group has investigated mechanisms of
central sensitization of nociceptive neurons by examining the
responses to intradermal injection of capsaicin. These experiments
are pertinent to issues raised by coderre & katz (sect. 2).