PMID: 8822575 [PubMed - indexed for MEDLINE]
Department of Physiology, University of North Carolina at Chapel Hill 27599-7545, USA.
1. The effects of ipsilateral removal of the superior cervical ganglion on the subsequent
responsiveness of C-fiber polymodal nociceptors (CPMs) of the ear to close-arterial
injections of norepinephrine (NE) were evaluated in adult, anesthetized rabbits. 2. In
normal unanesthetized rabbits, the two ears were usually at the same temperature.
Immediately after the ganglionectomy, the ipsilateral ear was warmer; however, at the
time of electrophysiological recordings (4-23 days) the majority of animals had the
ipsilateral ear cooler by > or = 1 degree C, suggestive of denervation supersensitivity. 3.
NE (50 ng) did not activate any CPMs (n = 28) from intact animals. 4. Seven of 22 CPMs
recorded from sympathectomized ears were activated by NE (50 ng). The responses
varied considerably but typically consisted of 2-4 impulses in the 60 s after the NE
injection. In some instances, repetitive activity continued for many minutes. Such
prolonged discharge differs from the adrenergic responses seen after partial nerve
damage. 5. The induction of adrenergic excitability in CPMs by sympathectomy is
suggested to be a counterpart to postsympathectomy neuralgia in human beings and a
possible part of the mechanism leading to sympathetically related pain states.
