Cutaneous vascular responses evoked by noxious stimulation in rats with the spinal nerve ligation-induced model of neuropathy.
Antidromic activation of nociceptive nerve fibres innervating the skin produces an axon reflex that involves extravasation and vasodilation of cutaneous blood vessels. We determined whether the axon reflex of the hindlimb skin is influenced by an experimental model of neuropathy induced by unilateral ligation of spinal nerves L(5) and L(6) in the rat. Ligation of spinal nerves induced symptoms mimicking tactile allodynia, as indicated by a marked decrease of the hindlimb withdrawal threshold to mechanical stimulation. The axon reflex induced by antidromic electrical stimulation of nociceptive fibres innervating the plantar skin ipsilateral to the ligation was attenuated according to determination of extravasation response and blood flow response. Lidocaine block or transection of the sciatic nerve of the neuropathic limb did not induce any change in basal blood flow of the plantar skin. The results indicate that ligation of spinal nerves induces an attenuation of the axon reflex. This attenuation reflects a decrease in the efferent function of primary afferent nociceptors innervating the hypersensitive skin of the hindpaw. The attenuation of antidromically-induced vascular responses was not caused by overriding sympathetic activity, as indicated by lack of blood flow effects by lidocaine blocks or a transection of the sciatic nerve.
Department of Physiology, Institute of Biomedicine, University of Helsinki, Helsinki, Finland.
Timo
T
Kauppila
Vesa K
VK
Kontinen
Hong
H
Wei
Erkki
E
Jyväsjärvi
Antti
A
Pertovaara
D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000502:physiology; D004396:Coloring Agents / Q000493:pharmacokinetics; D004558:Electric Stimulation; D005070:Evans Blue / Q000493:pharmacokinetics; D017078:Laser-Doppler Flowmetry; D008012:Lidocaine / Q000494:pharmacology; D008026:Ligation; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D017288:Pain Threshold / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000502:physiology; D012584:Sciatic Nerve / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000294:innervation*; D013127:Spinal Nerves / Q000503:physiopathology*; D014110:Touch / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
D000779:Anesthetics, Local; D004396:Coloring Agents; D005070:Evans Blue; D008012:Lidocaine