title: Selective elimination of isolectin B4-binding trigeminal neurons enhanced formalin-induced nocifensive behavior in the upper lip of rats and c-Fos expression in the trigeminal subnucleus caudalis.
abstract: The functional significance of non-peptidergic C-fibers in orofacial pain processing is largely unknown. The present study examined the effects of the selective elimination of isolectin B4 (IB4)-binding (IB4(+)) neurons on formalin-induced face rubbing behavior (FRB) in the upper lip of rats and c-Fos-immunoreactive (c-Fos-IR) cells in the trigeminal subnucleus caudalis (Vc). IB4 conjugated to neurotoxin, saporin (IB4-Sap), blank-saporin (Bl-Sap), or saline (Sal) was injected into the cisterna magna. IB4-Sap treatments significantly decreased IB4(+) terminals in lamina II of Vc and IB4(+) trigeminal ganglia neurons, whereas Sal- and BI-Sap treatments did not. The number of formalin-induced FRB 15-30 min after the formalin injection was significantly higher in IB4-Sap-treated rats than in Sal- or Bl-Sap-treated rats, and was associated with an increase in c-Fos-IR cells. The systemic preadministration of the GABAA antagonist, bicuculline, and agonist, muscimol, had stronger decreasing effects on FRB and c-Fos-IR cells in IB4-Sap-treated rats than the preadministration of Sal, whereas the opposite effects were observed in Sal- and Bl-Sap-treated rats. These results indicate that IB4(+) neurons in the trigeminal nerve play antinociceptive regulatory roles in formalin-induced orofacial pain processing and that GABAA receptor functions at segmental and supratrigeminal sites have complex modulatory influences on antinociceptive roles.
authors.affiliation: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Japan. Electronic address: a-ohyama@dent.osaka-u.ac.jp.
authors.forename: Aiko
authors.initials: A
authors.lastname: Oyamaguchi
authors.affiliation: Department of Dentistry and Oral Surgery, Hyogo College of Medicine, Japan. Electronic address: tetsu328@hyo-med.ac.jp.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Abe
authors.affiliation: Department of Acupuncture, Takarazuka University of Medical and Health Care, Japan. Electronic address: sugiyo@tumh.ac.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sugiyo
authors.affiliation: Department of Dental Anesthesiology, Osaka University Graduate School of Dentistry, Japan. Electronic address: niwa@dent.osaka-u.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Niwa
authors.affiliation: Department of Oral Anatomy, Osaka University Graduate School of Dentistry, Japan. Electronic address: takemura@dent.osaka-u.ac.jp.
authors.forename: Motohide
authors.initials: M
authors.lastname: Takemura
mesh_terms: D000818:Animals; D002946:Cisterna Magna; D037102:Lectins / Q000378:metabolism* / Q000494:pharmacology; D008046:Lip / Q000503:physiopathology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D010146:Pain / Q000378:metabolism / Q000503:physiopathology / Q000523:psychology*; D010147:Pain Measurement; D011485:Protein Binding; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D054789:Ribosome Inactivating Proteins, Type 1 / Q000494:pharmacology; D000076985:Saporins; D014275:Trigeminal Caudal Nucleus / Q000166:cytology / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000166:cytology / Q000378:metabolism
chemical_list: C496198:IB4-saporin conjugate; D037102:Lectins; D016760:Proto-Oncogene Proteins c-fos; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins
keywords: Formalin test; GABA(A); IB4; Saporin; c-Fos