Effects of Nerve Injury on Sympathetic Excitation of a Mechanical
Nociceptors.
Bossut, Daniel F., and Edward R. Perl.
Department of Physiology, University of North Carolina at Chapel Hill,
Chapel Hill, NC 27599.
APStracts 2:0052N, 1995.
SUMMARY AND CONCLUSIONS
1. The effects of sympathetic stimulation and close arterial injection of
norepinephrine were tested on cutaneous myelinated-fiber (A[delta]) mechanical
nociceptors (high threshold mechanoreceptors - MyHTMs) from normal and from
partially transsected nerves. 2. Neither sympathetic stimulation nor close
arterial injection of norepinephrine (200 ng) excited MyHTMs (18) recorded
from the uninjured great auricular nerve of adult rabbits. 3. MyHTMs (58)
conducting across the site of partial cut lesions, made 2 to 28 days
previously, had threshold and responsiveness to mechanical stimuli, receptive
field organization, and absence of background discharge typical of such
elements in normal nerve. 4. Four MyHTMs recorded from the injured nerves were
excited by sympathetic stimulation and/or norepinephrine injection but only
one gave more than two impulses within 60 sec to either form of stimulation.
5. The meagerness of the sympathetic and adrenergic excitation of MyHTMs after
nerve injury contrasts with that observed under similar conditions for C-fiber
polymodal nociceptors. Therefore, induction of adrenergic responsiveness in
nociceptors after partial denervation in cutaneous MyHTMs appears to be less
important for mechanisms related to pathogenic pain than alterations in
certain C-fiber nociceptors.
Received 14 November 1994; accepted in final form 19 January 1995.
APS Manuscript Number J716-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.