Interactions of sympathetic and primary afferent neurons following nerve injury and tissue trauma

This chapter concentrates on the mechanisms by which the sympathetic nervous system may be causally involved in the generation of pain and hyperalgesia following nerve lesion and of pain, hyperalgesia, and the neurogenic component during inflammation following tissue trauma. Emphasis is put on the possible differences in the mechanisms by which the sympathetic nervous system may be involved in pain following nerve trauma and pain following tissue trauma associated with inflammation. Several clinical observations indicate that the sympathetic nervous system may be involved in different pain states. The chapter describes clinical observations that support this idea for patients with sympathetically maintained pain following nerve trauma and patients with pain during inflammation not associated with overt nerve injury. It has been experimentally shown that the sympathetic post-ganglionic neurons supplying skin and synovium have important functions in the sensitization and activation of primary afferent neurons, as well as in neurogenic inflammation under pathophysiological conditions. These peripheral functions of the post-ganglionic neurons are under control of the central nervous system. © 1996 Elsevier Science B.V. All rights reserved.