title: Neural mechanism underlying hyperalgesic response to orofacial pain in Parkinson's disease model rats.
abstract: To investigate the neural mechanism of pain originating from the orofacial region in PD patients, we used PD model rats produced by unilateral injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. We investigated effects of nigrostriatal lesions on the behavioral response (face rubbing) to formalin injection into the upper lip. We also examined expression of c-Fos and phosphorylated extracellular signal-regulated kinase (pERK) in the trigeminal spinal subnucleus caudalis (Vc) and expression of c-Fos in the periaqueductal gray matter (PAG). Face rubbings following formalin injection showed a biphasic profile, with the first phase for the first 5 min and the second phase from 10 to 90 min. Rats with 6-OHDA lesions showed increased face rubbings in the second phase when formalin was injected ipsilaterally to the lesion, and c-Fos expression in the Vc increased. When formalin was injected contralaterally, face rubbings were reduced in the first phase, however, expression levels of c-Fos and pERK in the Vc were unchanged. No significant difference was found in c-Fos expression in the PAG between 6-OHDA- and saline-injected rats. These results suggest that unilateral dopamine depletion in the nigrostriatal pathway may be involved in hypersensitivity to noxious stimulation delivered to the orofacial region.
authors: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan. Electronic address: maegawa@dent.osaka-u.ac.jp.
authors: Hiroharu
authors: H
authors: Maegawa
authors: Special Patient Oral Care Unit, Kyushu University Hospital, Fukuoka, Fukuoka 812-8582, Japan.
authors: Yoshinari
authors: Y
authors: Morimoto
authors: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Chiho
authors: C
authors: Kudo
authors: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Hiroshi
authors: H
authors: Hanamoto
authors: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Aiji
authors: A
authors: Boku
authors: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Mitsutaka
authors: M
authors: Sugimura
authors: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Takafumi
authors: T
authors: Kato
authors: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Atsushi
authors: A
authors: Yoshida
authors: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors: Hitoshi
authors: H
authors: Niwa
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D005157:Facial Pain / Q000139:chemically induced / Q000150:complications*; D005557:Formaldehyde / Q000633:toxicity; D006930:Hyperalgesia / Q000209:etiology* / Q000378:metabolism; D008297:Male; D016627:Oxidopamine / Q000633:toxicity; D010300:Parkinson Disease / Q000150:complications* / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D005557:Formaldehyde; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase
keywords: 6-Hydroxydopamine; Formalin; Medial forebrain bundle; Parkinson's disease; Periaqueductal gray matter; Trigeminal spinal subnucleus caudalis; Tyrosine hydroxylase; c-Fos