title: Participation of peripheral group I and II metabotropic glutamate receptors in the development or maintenance of IL-1beta-induced mechanical allodynia in the orofacial area of conscious rats.
abstract: The present study investigated the role of peripheral groups I and II metabotropic glutamate receptors (mGluRs) in interleukin (IL)-1beta-induced mechanical allodynia in the orofacial area of rats. Subcutaneous injection of 10 pg of IL-1beta decreased air-puff thresholds ipsilateral or contralateral to the injection site. The decrease in air-puff thresholds appeared 10 min after the injection of IL-1beta and IL-1beta-induced mechanical allodynia persisted for over 3 h. Pre-treatment with 7-(hydroxyimino) cyclopropa[b] chromen-1a-carboxylate ethyl ester (CPCCOEt) or 2-methyl-6-(phenylethynyl)-pyridine hydrochloride (MPEP), a mGluR1 or mGluR5 antagonist, blocked IL-1beta-induced mechanical allodynia and mirror-image mechanical allodynia produced by a subcutaneous injection of 10 pg of IL-1beta. However, post-treatment with CPCCOEt or MPEP did not affect changes in behavioral responses, which were produced by the IL-1beta injection. Pre-treatment, as well as post-treatment with (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC), a group II mGluR agonist, blocked either IL-1beta-induced mechanical allodynia or mirror-image mechanical allodynia. The anti-allodynic effects of APDC were abolished by pre-treatment with (2S)-2-amino-2[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495), a group II mGluR antagonist. These results indicate that peripheral group II mGluRs are involved in the development and maintenance of IL-1beta-induced mechanical allodynia, while peripheral group I mGluRs are involved in the development of IL-1beta-induced mechanical allodynia. Based on our observations, the peripheral application of group II mGluR agonists may be of therapeutic value in treating inflammatory pain.
authors.affiliation: Department of Oral Physiology and BrainKorea 21, School of Dentistry, Kyungpook University, Daegu, South Korea.
authors.forename: Chang Y
authors.initials: CY
authors.lastname: Jung
authors.forename: Sang Y
authors.initials: SY
authors.lastname: Lee
authors.forename: Hyo S
authors.initials: HS
authors.lastname: Choi
authors.forename: Eun J
authors.initials: EJ
authors.lastname: Lim
authors.forename: Min K
authors.initials: MK
authors.lastname: Lee
authors.forename: Gwi Y
authors.initials: GY
authors.lastname: Yang
authors.forename: Seung R
authors.initials: SR
authors.lastname: Han
authors.forename: Dong H
authors.initials: DH
authors.lastname: Youn
authors.forename: Dong K
authors.initials: DK
authors.lastname: Ahn
mesh_terms: D000818:Animals; D003243:Consciousness; D005157:Facial Pain / Q000139:chemically induced / Q000378:metabolism*; D006941:Hyperesthesia / Q000139:chemically induced / Q000378:metabolism*; D053583:Interleukin-1beta; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D014110:Touch / Q000187:drug effects*
chemical_list: D053583:Interleukin-1beta; D018094:Receptors, Metabotropic Glutamate; C108822:metabotropic glutamate receptor 2; C104077:metabotropic glutamate receptor type 1