title: Novel methods of applying direct chemical and mechanical stimulation to the oral mucosa for traditional behavioral pain assays in conscious rats.
abstract: BACKGROUND
  Stomatitis induces severe and painful hypersensitivity to pungency and physical contact during meals. Many studies have used anesthetized animals to examine evoked nociception in the oral mucosa, but no reports have used traditional behavioral assays to evaluate nociception in conscious animals.
  
  
  METHODS
  We developed two new methods of applying chemical or mechanical stimulation directly to the oral mucosa of the mandibular vestibule of conscious rats. Nociceptive evaluations were performed by measuring facial grooming time and the head withdrawal threshold to von Frey stimulations. (1) For the intraoral dropping method, rat mucosa was transiently exposed by hand, and a drop of a pungent solution was applied. (2) For the stable intraoral opening method, rat mucosa was long-term exposed following piercing surgery of the mental skin after habitual training for 2-3 weeks.
  
  
  RESULTS
  In the intraoral dropping method, the application of 100 μM capsaicin or 100 mM allyl isothiocyanate prolonged mouth-rubbing time. Capsaicin-induced mouth-rubbing time was further enhanced following the development of an acetic acid-induced ulcer. The stable intraoral opening method enabled stable measurements of the mechanical withdrawal threshold in the oral mucosa of conscious rats. Ulcer development decreased the mechanical threshold, whereas topical lidocaine treatment increased the threshold.
  
  
  METHODS
  These new methods enable the evaluations of motivational nocifensive behaviors in response to intraoral stimulations without any anesthetic effects.
  
  
  CONCLUSIONS
  The intraoral dropping and stable intraoral opening methods can be used in combination with traditional behavioral assays to evaluate nociception in the oral mucosa of conscious rats.
authors.affiliation: Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan. Electronic address: r11hitomi@fa.kyu-dent.ac.jp.
authors.forename: Suzuro
authors.initials: S
authors.lastname: Hitomi
authors.affiliation: Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan. Electronic address: ono@kyu-dent.ac.jp.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ono
authors.affiliation: Division of Cancer Pathophysiology, National Cancer Center Research Institute, 5-1-1, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. Electronic address: kmiyano@ncc.go.jp.
authors.forename: Kanako
authors.initials: K
authors.lastname: Miyano
authors.affiliation: Division of Dentistry and Oral Surgery, Shizuoka Cancer Center Hospital and Research Institute, 1007 Shimonagakubo, Nagaizumi-cho, Sunto-gun, Shizuoka 411-8777, Japan.
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Ota
authors.affiliation: Division of Cancer Pathophysiology, National Cancer Center Research Institute, 5-1-1, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. Electronic address: yuezono@ncc.go.jp.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Uezono
authors.affiliation: Division of Palliative Medicine and Psycho-Oncology Palliative Care Team, National Cancer Center, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Matoba
authors.affiliation: Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Kuramitsu
authors.affiliation: Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan; Division of Dental Anesthesiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580, Japan. Electronic address: letiziare.une.524@gmail.com.
authors.forename: Kiichiro
authors.initials: K
authors.lastname: Yamaguchi
authors.affiliation: Division of Pathology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan. Electronic address: kou@kyu-dent.ac.jp.
authors.forename: Kou
authors.initials: K
authors.lastname: Matsuo
authors.affiliation: Division of Anatomy, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan. Electronic address: yujiseta@kyu-dent.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Seta
authors.affiliation: Division of Dental Anesthesiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580, Japan. Electronic address: harano@kyu-dent.ac.jp.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Harano
authors.affiliation: Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan. Electronic address: ine@kyu-dent.ac.jp.
authors.forename: Kiyotoshi
authors.initials: K
authors.lastname: Inenaga
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000009:adverse effects; D003243:Consciousness; D006120:Grooming / Q000187:drug effects; D006930:Hyperalgesia / Q000175:diagnosis / Q000209:etiology; D017879:Isothiocyanates / Q000009:adverse effects; D008297:Male; D009061:Mouth Mucosa / Q000187:drug effects / Q000294:innervation*; D010146:Pain / Q000175:diagnosis* / Q000209:etiology*; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000294:innervation; D013268:Stimulation, Chemical; D013997:Time Factors
chemical_list: D017879:Isothiocyanates; C004471:allyl isothiocyanate; D002211:Capsaicin
keywords: Conscious rats; Facial grooming; Head withdrawal threshold to von Frey stimulation; Intraoral evoked pain; Oral ulcer