title: Differential responses of rostral subnucleus caudalis and upper cervical dorsal horn neurons to mechanical and chemical stimulation of the parotid gland in rats.
abstract: Blockage of the salivary duct can produce pain and inflammation from the build up of saliva in the parotid gland. The processing of parotid inflammation-induced pain, however, is poorly understood. The purpose of this study was to clarify the functional involvement of the trigeminal subnucleus interpolaris/caudalis transition region (Vi/Vc) and upper cervical spinal cord (C1/C2) in processing nociceptive input relevant to parotitis. The effect of capsaicin-induced parotitis was examined on a total of 37 nociceptive neurons isolated from the Vi/Vc (n = 23) and C1/C2 (n = 14) regions. Eight of 23 Vi/Vc neurons responded to mechanical distention of the parotid gland, whereas no C1/C2 neurons responded to the parotid distention. Receptive field characteristics in all neurons were examined following capsaicin injections into the parotid gland. Mechanical and cold responses increased significantly in C1/C2 but not Vi/Vc neurons following capsaicin. Receptive field sizes also increased in C1/C2 but not Vi/Vc neurons. At the Vi/Vc transition region, pinch-evoked activity increased in neurons receiving convergent inputs from the parotid gland and facial skin when compared to non-convergent neurons. The present data indicate that the hyperalgesia and referred pain associated with parotitis may result from sensitization of C1/C2, but not Vi/Vc nociceptive neurons.
authors.affiliation: Department of Oral Diagnosis, School of Dentistry, Nihon University, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Oral Diagnosis, School of Dentistry, Nihon University, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan. Electronic address: ogawa-a@dent.nihon-u.ac.jp.
authors.forename: Akiko
authors.initials: A
authors.lastname: Ogawa
authors.affiliation: Division of Clinical Research, Dental Research Center, Nihon University School of Dentistry, Tokyo 101-8310, Japan; Department of Physiology, College of Osteopathic Medicine, University of New England, 11 Hills Beach Rd., Biddeford, ME 04005, USA.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Meng
authors.affiliation: Department of Physiology, College of Osteopathic Medicine, University of New England, 11 Hills Beach Rd., Biddeford, ME 04005, USA; Department of Biomedical Sciences, University of Maryland Dental School, Baltimore, Maryland 21201, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Ren
authors.affiliation: Department of Oral Diagnosis, School of Dentistry, Nihon University, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Division of Clinical Research, Dental Research Center, Nihon University School of Dentistry, Tokyo 101-8310, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Imamura
authors.affiliation: Department of Physiology, School of Dentistry, Nihon University, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo 101-8310, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwata
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002574:Cervical Vertebrae; D003080:Cold Temperature / Q000009:adverse effects; D006930:Hyperalgesia / Q000139:chemically induced / Q000503:physiopathology; D018836:Inflammation Mediators / Q000494:pharmacology; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010306:Parotid Gland / Q000294:innervation* / Q000503:physiopathology; D010309:Parotitis / Q000139:chemically induced / Q000503:physiopathology; D010812:Physical Stimulation; D020671:Posterior Horn Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000294:innervation / Q000503:physiopathology; D014275:Trigeminal Caudal Nucleus / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*
chemical_list: D018836:Inflammation Mediators; D002211:Capsaicin