Alterations in myelinated fibres in the sciatic nerve of rats after constriction: possible relationships between the presence of abnormal small myelinated fibres and pain-related behaviour.
Morphology or peripheral myelinated fibres was analyzed in rats exhibiting hyperalgesia and allodynia with mechanical and thermal stimuli, consecutive to a mononeuropathy induced by 4 loose ligatures around a sciatic nerve. This preliminary study was based on weeks 2-3 after surgery, the time of the maximum alterations of the pain-related behaviour. At this time, contrasting with a marked decrease of the large afferent fibres a consistent number of much less than 5 micron fibres was pointed out. In addition to their extremely short internodal length, the majority of these fibres had an abnormal g-ratio, thus an abnormal myelin sheath. It is suggested that this group of abnormal fibres might be related to the A delta fibres described in neuromas and involved in pain-related behaviours seen in the mononeuropathic rats.
Gautron
M
M
Unité de Recherches de Physiopharmacologié du systeme nerveux, INSERM U 1610, Paris, France.
Jazat
F
F
Ratinahirana
H
H
Hauw
J J
JJ
Guilbaud
G
G
D000818:Animals; D008297:Male; D009186:Myelin Sheath / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012584:Sciatic Nerve / Q000503:physiopathology*; D014855:Wallerian Degeneration