Sympathectomy induces adrenergic excitability of cutaneous C-fiber nociceptors.
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.
Bossut
D F
DF
Department of Physiology, University of North Carolina at Chapel Hill 27599-7545, USA.
Shea
V K
VK
Perl
E R
ER
D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D004431:Ear, External / Q000294:innervation; D005260:Female; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology*; D009638:Norepinephrine / Q000502:physiology; D018408:Patch-Clamp Techniques; D011817:Rabbits; D012867:Skin / Q000294:innervation*; D012881:Skin Temperature / Q000502:physiology; D017783:Superior Cervical Ganglion / Q000502:physiology*; D013562:Sympathectomy; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology
D009638:Norepinephrine