Blockade of peripheral 5HT3 receptor attenuates the formalin-induced nocifensive behavior in persistent temporomandibular joint inflammation of rat.
The role of peripheral 5HT3 receptors in the orofacial nocifensive behavior induced by the injection of formalin into masseter muscle was evaluated. The behavioral activities evoked by the formalin injection exhibited a biphasic response in the rats with or without temporomandibular joint (TMJ) inflammation (CFA group or non-CFA group). The orofacial nocifensive behavioral activity was enhanced after TMJ inflammation. Systemic administration of tropisetron, 5HT3 receptor antagonist, reduced the nocifensive behavioral activities in the late phase of orofacial formalin test in CFA group, but not in non-CFA group. Local administration of tropisetron into the masseter muscle in CFA group, but not in non-CFA group also attenuated the behavioral activities in the late phase. Unexpectedly, low dose of local tropisetron reduced the nocifensive behavioral activities in the early phase of orofacial formalin test in CFA group. These data suggest that induction of TMJ inflammation causes the elevation of the orofacial nocifensive behavioral activities evoked by formalin injection into masseter muscle, and that peripheral 5HT3 receptors may play a critical role in nociception and the transmission of orofacial pain.
Department of Anatomy and Neurobiology, Wakayama Medical University, Kimiidera 811-1, Wakayama City 640-0012, Japan.
Keiichiro
K
Okamoto
Hiroki
H
Imbe
Akimasa
A
Tashiro
Shunji
S
Kumabe
Emiko
E
Senba
D000818:Animals; D001522:Behavior, Animal; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D005157:Facial Pain / Q000139:chemically induced / Q000188:drug therapy*; D005557:Formaldehyde; D005620:Freund's Adjuvant; D007211:Indoles / Q000627:therapeutic use*; D007249:Inflammation / Q000139:chemically induced / Q000503:physiopathology; D008297:Male; D010147:Pain Measurement / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D044406:Receptors, Serotonin, 5-HT3 / Q000187:drug effects / Q000502:physiology; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists / Q000627:therapeutic use; D013705:Temporomandibular Joint Disorders / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology; D013997:Time Factors; D000077526:Tropisetron
D007211:Indoles; D044406:Receptors, Serotonin, 5-HT3; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists; D005557:Formaldehyde; D000077526:Tropisetron; D005620:Freund's Adjuvant