Pain and death: neurodegenerative disease mechanisms in the nociceptor.

Chronic peripheral neuropathic pain is the result of abnormal activity in sensory nerves. It is well recognized that this sensory nerve dysfunction can be caused by traumatic, toxic, or metabolic insult to the nerve. In addition, there is growing recognition that neuropathic pain is a frequent manifestation of neurodegenerative diseases. In this regard, important clues to the cellular mechanisms of neuropathic pain may be found by close examination of neurodegenerative diseases (including Parkinson's disease) in which neuropathic pain is often an underappreciated but important clinical manifestation. This approach identifies specific mitochondrial and cytoskeletal mechanisms, previously implicated in the pathophysiology of neurodegenerative diseases in the central nervous system, that might contribute to neuropathic dysfunction in peripheral sensory nerve fibers. Investigations in preclinical models of common peripheral neuropathic pain conditions have supported the idea that a subset of these cellular mechanisms of neurodegeneration can produce painful hyperactivity in primary afferent nociceptors. Importantly, this emerging concept of neurodegenerative disease mechanisms in the primary afferent nociceptor identifies novel molecular targets for the treatment neuropathic pain.