title: Effects of intracisternal injection of interleukin-6 on nociceptive jaw opening reflex and orofacial formalin test in freely moving rats.
abstract: The present study was performed to investigate the effects of central cytokines on the modulation of nociception in the orofacial area. To achieve this purpose, a nociceptive jaw opening reflex and an orofacial formalin test were monitored before and after intracisternal administration of interleukin-6 (IL-6) in freely moving rats. In the nociceptive jaw opening reflex, the digastric electromyogram (dEMG) was not significantly changed after intracisternal injection of 200 pg and 2 ng IL-6. However, 20 ng IL-6 suppressed dEMG to 74+/-7% of the control values. In the inflammatory orofacial formalin test, intracisternal injection of 200 pg and 2 ng IL-6 did not change the number of noxious behavioral responses produced by formalin injection. However, 20 ng IL-6 injected intracisternally significantly increased the number of noxious behavioral responses produced by formalin. The hyperalgesic action of intracisternal IL-6 in the orofacial formalin test was blocked by pretreatment with interleukin-1 (IL-1) receptor antagonist. These results suggest that IL-6 injected intracisternally modulates the transmission of nociceptive information in the orofacial area. However, the hypo/hyper-algesic response of central cytokines seems to depend on the orofacial pain model. The hyperalgesic response of central IL-6 seems to be mediated by the IL-1 receptor.
authors.affiliation: Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu, South Korea.
authors.forename: Hyo-Soon
authors.initials: HS
authors.lastname: Choi
authors.forename: Jin-Sook
authors.initials: JS
authors.lastname: Ju
authors.forename: Ho-Jeong
authors.initials: HJ
authors.lastname: Lee
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Kim
authors.forename: Jae-Sik
authors.initials: JS
authors.lastname: Park
authors.forename: Dong-Kuk
authors.initials: DK
authors.lastname: Ahn
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D004576:Electromyography; D005557:Formaldehyde / Q000494:pharmacology; D006930:Hyperalgesia / Q000503:physiopathology; D053590:Interleukin 1 Receptor Antagonist Protein; D015850:Interleukin-6 / Q000008:administration & dosage / Q000494:pharmacology*; D007568:Jaw / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008410:Masticatory Muscles / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors; D012018:Reflex / Q000187:drug effects* / Q000502:physiology; D012795:Sialoglycoproteins / Q000494:pharmacology
chemical_list: D053590:Interleukin 1 Receptor Antagonist Protein; D015850:Interleukin-6; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins; D005557:Formaldehyde