Behavioral changes and trigeminal ganglion sodium channel regulation in an orofacial neuropathic pain model.
We used a photochemical method to generate a partial ischemic injury to the infraorbital branch of the trigeminal nerve in rats. Following injury, rats developed a bilateral persistent hypersensitivity to mechanical stimulation in the territory innervated by the infraorbital nerve. In addition, spread of mechanical hypersensitivity beyond the facial region was noted. Heat hypersensitivity was also present, although to a lesser extent and of a shorter duration. In some rats, excessive facial grooming/scratching were observed. Morphological examination revealed a graded damage to the irradiated portion of the infraorbital nerve that was related to the duration of laser irradiation. Investigations of gene expression changes in injured trigeminal ganglion neurons of animals with behavioral signs of neuropathic pain demonstrated that the sodium channel alpha-subunit Na(v)1.3-absent in sham-operated animals-was expressed to a limited extent. mRNAs for Na(v)1.8 and Na(v)1.9 were reduced both with respect to proportions of expressing neurons and to intensities, whereas the beta 3 subunit was markedly upregulated. mRNA levels of p11, a regulatory factor that facilitates the surface expression of Na(v)1.8, were unchanged. Previous findings have shown that injury to the trigeminal nerve branches may elicit responses that differ from those of segmental spinal nerves. Despite this we conclude that the key sodium channel regulations that are reported as consequences of nerve damage in the dorsal root ganglia seem to appear also in the trigeminal ganglion. Thus, novel analgesic drugs designed to target the sodium channel subtypes involved could be of use for the treatment of orofacial pain.
Eriksson
Jonas
J
Center for Oral Biology, Novum, Karolinska Institutet, P.O. Box 4064, S-141 04 Huddinge, Sweden Department of Clinical Neuroscience, Section of Clinical Neurophysiology, Karolinska University Hospital Huddinge, S-141 86 Huddinge, Sweden.
Jablonski
Aleksandra
A
Persson
Anna-Karin
AK
Hao
Jing-Xia
JX
Kouya
Poli Francois
PF
Wiesenfeld-Hallin
Zsuzsanna
Z
Xu
Xiao-Jun
XJ
Fried
Kaj
K
D000222:Adaptation, Physiological; D000818:Animals; D004195:Disease Models, Animal; D005157:Facial Pain / Q000150:complications / Q000503:physiopathology*; D006941:Hyperesthesia / Q000150:complications / Q000503:physiopathology*; D008297:Male; D001523:Mental Disorders / Q000209:etiology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000378:metabolism*
D015222:Sodium Channels