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Recent evidence for activity-dependent initiation of sympathetic sprouting and neuropathic pain

Jun-Ming ZHANG*, Judith A. Strong

Department of Anesthesiology, University of Cincinnati College of Medicine 231 Albert Sabin Way, Cincinnati, OH 45267-0531, USA

摘要

Traumatic injury or inflammatory irritation of the peripheral nervous system often leads to persistent pathophysiologicalpain states. It has been well-documented that, after peripheral nerve injury or inflammation, functional and anatomical alterationssweep over the entire peripheral nervous system including the peripheral nerve endings, the injured or inflamed afferent fibers, thedorsal root ganglion (DRG), and the central afferent terminals in the spinal cord. Among all the changes, ectopic discharge orspontaneous activity of primary sensory neurons is of great clinical interest, as such discharges doubtless contribute to the developmentof pathological pain states such as neuropathic pain. Two key sources of abnormal spontaneous activity have been identifiedfollowing peripheral nerve injury: the injured afferent fibers (neuroma) leading to the DRG, and the DRG somata. The purpose of thisreview is to provide a global account of the abnormal spontaneous activity in various animal models of pain. Particular attention isfocused on the consequence of peripheral nerve injury and localized inflammation. Further, mechanisms involved in the generation ofspontaneous activity are also reviewed; evidence of spontaneous activity in contributing to abnormal sympathetic sprouting in theaxotomized DRG and to the initiation of neuropathic pain based on new findings from our research group are discussed. An improvedunderstanding of the causes of spontaneous activity and the origins of neuropathic pain should facilitate the development of novelstrategies for effective treatment of pathological pain.

关键词： neuropathic pain; spared nerve injury; chronic constriction injury; ectopic activity; sympathetic sprouting; allodynia; hyperalgesia

Recent evidence for activity-dependent initiation of sympathetic sprouting and neuropathic pain

Jun-Ming ZHANG*, Judith A. Strong

Department of Anesthesiology, University of Cincinnati College of Medicine 231 Albert Sabin Way, Cincinnati, OH 45267-0531, USA

Abstract

Traumatic injury or inflammatory irritation of the peripheral nervous system often leads to persistent pathophysiologicalpain states. It has been well-documented that, after peripheral nerve injury or inflammation, functional and anatomical alterationssweep over the entire peripheral nervous system including the peripheral nerve endings, the injured or inflamed afferent fibers, thedorsal root ganglion (DRG), and the central afferent terminals in the spinal cord. Among all the changes, ectopic discharge orspontaneous activity of primary sensory neurons is of great clinical interest, as such discharges doubtless contribute to the developmentof pathological pain states such as neuropathic pain. Two key sources of abnormal spontaneous activity have been identifiedfollowing peripheral nerve injury: the injured afferent fibers (neuroma) leading to the DRG, and the DRG somata. The purpose of thisreview is to provide a global account of the abnormal spontaneous activity in various animal models of pain. Particular attention isfocused on the consequence of peripheral nerve injury and localized inflammation. Further, mechanisms involved in the generation ofspontaneous activity are also reviewed; evidence of spontaneous activity in contributing to abnormal sympathetic sprouting in theaxotomized DRG and to the initiation of neuropathic pain based on new findings from our research group are discussed. An improvedunderstanding of the causes of spontaneous activity and the origins of neuropathic pain should facilitate the development of novelstrategies for effective treatment of pathological pain.

Key words: neuropathic pain; spared nerve injury; chronic constriction injury; ectopic activity; sympathetic sprouting; allodynia; hyperalgesia

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引用本文：

Jun-Ming ZHANG*, Judith A. Strong. Recent evidence for activity-dependent initiation of sympathetic sprouting and neuropathic pain[J]. 生理学报 2008; 60 (5): 617-627.

Jun-Ming ZHANG*, Judith A. Strong. Recent evidence for activity-dependent initiation of sympathetic sprouting and neuropathic pain. Acta Physiol Sin 2008; 60 (5): 617-627 (in Chinese with English abstract).