title: Involvement of trigeminal transition zone and laminated subnucleus caudalis in masseter muscle hypersensitivity associated with tooth inflammation.
abstract: A rat model of pulpitis/periapical periodontitis was used to study mechanisms underlying extraterritorial enhancement of masseter response associated with tooth inflammation. Periapical bone loss gradually increased and peaked at 6 weeks after complete Freund's adjuvant (CFA) application to the upper molar tooth pulp (M1). On day 3, the number of Fos-immunoreactive (IR) cells was significantly larger in M1 CFA rats compared with M1 vehicle (veh) rats in the trigeminal subnucleus interpolaris/caudalis transition zone (Vi/Vc). The number of Fos-IR cells was significantly larger in M1 CFA and masseter (Mass) capsaicin applied (M1 CFA/Mass cap) rats compared with M1 veh/Mass veh rats in the contralateral Vc and Vi/Vc. The number of phosphorylated extracellular signal-regulated kinase (pERK)-IR cells was significantly larger in M1 CFA/Mass cap and M1 veh/Mass cap rats compared to Mass-vehicle applied rats with M1 vehicle or CFA in the Vi/Vc. Pulpal CFA application caused significant increase in the number of Fos-IR cells in the Vi/Vc but not Vc on week 6. The number of pERK-IR cells was significantly lager in the rats with capsaicin application to the Mass compared to Mass-vehicle treated rats after pulpal CFA- or vehicle-application. However, capsaicin application to the Mass did not further affect the number of Fos-IR cells in the Vi/Vc in pulpal CFA-applied rats. The digastric electromyographic (d-EMG) activity after Mass-capsaicin application was significantly increased on day 3 and lasted longer at 6 weeks after pulpal CFA application, and these increase and duration were significantly attenuated by i.t. PD98059, a MEK1 inhibitor. These findings suggest that Vi/Vc and Vc neuronal excitation is involved in the facilitation of extraterritorial hyperalgesia for Mass primed with periapical periodontitis or acute pulpal-inflammation. Furthermore, phosphorylation of ERK in the Vi/Vc and Vc play pivotal roles in masseter hyperalgesia after pulpitis or periapical periodontitis.
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan; Divisions of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Department of Radiology, Nihon University School of Dentistry, Tokyo, Japan; Divisions of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kunihito
authors.initials: K
authors.lastname: Matsumoto
authors.affiliation: Department of Oral Diagnosis, Nihon University School of Dentistry, Tokyo, Japan; Divisions of Clinical Research, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Noboru
authors.initials: N
authors.lastname: Noma
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsuura
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kinuyo
authors.initials: K
authors.lastname: Ohara
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Komiya
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Watase
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan; Divisions of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Bunnai
authors.initials: B
authors.lastname: Ogiso
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan; Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tsuboi
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan; Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Shinoda
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan; Divisions of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Hatori
authors.affiliation: Department of Oral Diagnosis, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Nakaya
authors.affiliation: Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan; Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan; Division of Applied System Neuroscience Advanced Medical Research Center, Nihon University Graduate School of Medical Science, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwata
mesh_terms: D000818:Animals; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008406:Masseter Muscle / Q000378:metabolism / Q000473:pathology*; D010485:Periapical Periodontitis / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014076:Tooth Diseases / Q000378:metabolism / Q000473:pathology*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D048049:Extracellular Signal-Regulated MAP Kinases