Spinal cord hyperexcitability and its role in pain and hyperalgesia.
Sensitization of spinal cord nociceptive neurons is commonly interpreted as the cause for the hypersensitivity that characterizes chronic pain states in humans. However, in spite of much basic research in this area it has not been possible to demonstrate a direct link between the hyperexcitability of spinal cord neurons observed experimentally and the underlying mechanism of a chronic pain state. The word sensitization is also used in the literature with various and different meanings from the qualification of a cellular process of enhanced excitability at synaptic level to the characteristics of a chronic pain syndrome. In this article the various meanings of sensitization are described and the relevance of the hyperexcitability of spinal cord neurons to the generation of clinically relevant pain states is discussed. A proposal is made to restrict the use of the word sensitization to the cellular process of enhanced excitability observed experimentally after repetitive stimulation of nociceptive afferents. Caution is also recommended when associating neuronal sensitization in the spinal cord with the mechanisms of chronic pain conditions.
Anesthesia Research Unit, Faculty of Medicine, Alan Edwards Center for Research on Pain, McGill University, McIntyre Medical Bldg. Room 1207, 3655 Promenade Sir William Osler, Montreal, QC H3G 1Y6, Canada. fernando.cervero@mcgill.ca
Fernando
F
Cervero
D000200:Action Potentials; D000818:Animals; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D013116:Spinal Cord / Q000503:physiopathology*
D018040:Receptors, Neurokinin-1