title: Aberrant TRPV1 expression in heat hyperalgesia associated with trigeminal neuropathic pain.
abstract: Trigeminal neuropathic pain is a facial pain syndrome associated with trigeminal nerve injury. However, the mechanism of trigeminal neuropathic pain is poorly understood. This study aimed to determine the role of transient receptor potential vanilloid 1 (TRPV1) in heat hyperalgesia in a trigeminal neuropathic pain model. We evaluated nociceptive responses to mechanical and heat stimuli using a partial infraorbital nerve ligation (pIONL) model. Withdrawal responses to mechanical and heat stimuli to vibrissal pads (VP) were assessed using von Frey filaments and a thermal stimulator equipped with a heat probe, respectively. Changes in withdrawal responses were measured after subcutaneous injection of the TRP channel antagonist capsazepine. In addition, the expression of TRPV1 in the trigeminal ganglia was examined. Mechanical allodynia and heat hyperalgesia were observed in VP by pIONL. Capsazepine suppressed heat hyperalgesia but not mechanical allodynia. The number of TRPV1-positive neurons in the trigeminal ganglia was significantly increased in the large-diameter-cell group. These results suggest that TRPV1 plays an important role in the heat hyperalgesia observed in the pIONL model.
authors.affiliation: Institute for Oral Science, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Urano
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ara
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Fujinami
authors.forename: B Yukihiro
authors.initials: BY
authors.lastname: Hiraoka
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D006358:Hot Temperature; D006930:Hyperalgesia / Q000235:genetics*; D007150:Immunohistochemistry; D008297:Male; D010146:Pain / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000235:genetics*; D014277:Trigeminal Neuralgia / Q000235:genetics*
chemical_list: D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat
keywords: TRPV1; heat hyperalgesia.; trigeminal neuropathic pain