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Autonomic fibre sprouting and changes in nociceptive sensory innervation in the rat lower lip skin following chronic constriction injury
Author(s) -
Grelik C.,
Bennett G. J.,
RibeirodaSilva A.
Publication year - 2005
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2005.04089.x
Subject(s) - calcitonin gene related peptide , sprouting , nociception , medicine , trigeminal ganglion , nerve injury , neuropathic pain , tropomyosin receptor kinase a , constriction , stimulation , sensory system , anesthesia , sensory nerve , autonomic nerve , nerve growth factor , endocrinology , neuroscience , receptor , neuropeptide , biology , botany
In this study we used immunocytochemistry to investigate whether autonomic fibres sprouted in the skin of the lower lip in a rat model of neuropathic pain. We used a bilateral chronic constriction injury (CCI) of the mental nerve (MN), a branch of the trigeminal nerve. In this model, we also studied the accompanying changes in peptidergic [calcitonin gene‐related peptide (CGRP)‐immunoreactive] sensory fibres, as well as in trkA receptor immunoreactivity in the sensory nerves. Autonomic (sympathetic and parasympathetic) fibre sprouting was first observed 1 week post‐injury with a peak in the number of sprouted fibres occurring at 4 and 6 weeks post‐CCI. CGRP‐IR fibres almost disappeared at 2 weeks post‐CCI, but quickly sprouted, leading to a significant peak above sham levels 4 weeks post‐injury. trkA receptor expression was found to be up‐regulated in small cutaneous nerves 4 weeks post‐CCI, returning to sham levels by 8 weeks post‐CCI. There was no sympathetic fibre sprouting in the trigeminal ganglion following CCI. At 4 weeks post‐CCI, rats displayed spontaneous, directed grooming to the area innervated by the MN that was not seen in sham animals, which we interpreted as a sign of spontaneous pain or dysesthesiae. Collectively, our findings indicate that as a result of autonomic sprouting due to CCI of the MN, remaining intact nociceptive fibres may potentially develop sensitivity to sympathetic and parasympathetic stimulation, which may have a role in the generation of abnormal pain following nerve injury.