title: TRPA1 contributes to capsaicin-induced facial cold hyperalgesia in rats.
abstract: Orofacial cold hyperalgesia is known to cause severe persistent pain in the face following trigeminal nerve injury or inflammation, and transient receptor potential (TRP) vanilloid 1 (TRPV1) and TRP ankylin 1 (TRPA1) are thought to be involved in cold hyperalgesia. However, how these two receptors are involved in cold hyperalgesia is not fully understood. To clarify the mechanisms underlying facial cold hyperalgesia, nocifensive behaviors to cold stimulation, the expression of TRPV1 and TRPA1 in trigeminal ganglion (TG) neurons, and TG neuronal excitability to cold stimulation following facial capsaicin injection were examined in rats. The head-withdrawal reflex threshold (HWRT) to cold stimulation of the lateral facial skin was significantly decreased following facial capsaicin injection. This reduction of HWRT was significantly recovered following local injection of TRPV1 antagonist as well as TRPA1 antagonist. Approximately 30% of TG neurons innervating the lateral facial skin expressed both TRPV1 and TRPA1, and about 64% of TRPA1-positive neurons also expressed TRPV1. The TG neuronal excitability to noxious cold stimulation was significantly increased following facial capsaicin injection and this increase was recovered by pretreatment with TRPA1 antagonist. These findings suggest that TRPA1 sensitization via TRPV1 signaling in TG neurons is involved in cold hyperalgesia following facial skin capsaicin injection.
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan; Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kuniya
authors.initials: K
authors.lastname: Honda
authors.forename: Masamichi
authors.initials: M
authors.lastname: Shinoda
authors.forename: Akihiko
authors.initials: A
authors.lastname: Furukawa
authors.forename: Kozue
authors.initials: K
authors.lastname: Kita
authors.forename: Noboru
authors.initials: N
authors.lastname: Noma
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwata
mesh_terms: D000083:Acetanilides / Q000494:pharmacology; D000813:Anilides / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal; D002211:Capsaicin / Q000009:adverse effects* / Q000494:pharmacology; D002934:Cinnamates / Q000494:pharmacology; D003080:Cold Temperature / Q000009:adverse effects*; D004576:Electromyography / Q000295:instrumentation; D005145:Face; D005157:Facial Pain / Q000209:etiology*; D006358:Hot Temperature / Q000009:adverse effects; D006930:Hyperalgesia / Q000209:etiology*; D007271:Injections, Intradermal; D008297:Male; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000737:chemistry / Q000187:drug effects; D010812:Physical Stimulation; D011687:Purines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D018689:Sensory System Agents / Q000009:adverse effects* / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D050916:TRPV Cation Channels / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology; D012668:Trigeminal Ganglion / Q000737:chemistry / Q000187:drug effects
chemical_list: C552888:2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide; D000083:Acetanilides; D000813:Anilides; D002934:Cinnamates; C477659:N-(3-methoxyphenyl)-4-chlorocinnamanilide; D011687:Purines; D018689:Sensory System Agents; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050916:TRPV Cation Channels; C480976:Trpa1 protein, rat; C493922:Trpv1 protein, rat; D002211:Capsaicin
keywords: orofacial pain; transient receptor potential ankylin 1; transient receptor potential vanilloid 1; trigeminal ganglion