The effects of blocking N/OFQ receptors on orofacial pain following experimental tooth movement in rats.

Objective: The aim of this study was to determine the effects of nociceptin/orphanin FQ peptide receptor (N/OFQ receptor) antagonist on orofacial pain induced by experimental tooth movement in rats. Methods: A total of 36 male Sprague-Dawley rats weighing 200-300 g were divided into six groups: a control group, force group, force+saline intraperitoneal group, force+saline periodontal group, force+UFP-101 ([Nphe',Arg' 4, Lys'5]1\l/OFQ-NH2; antagonist for N/OFQ receptor) intraperitoneal group, and force+UFP-101 periodontal group. Closed coil springs were ligated between the upper incisors and first molar to exert an orthodontic force (40 g) between the teeth. Injectable administration dosages were 30 pl saline or 30 pl saline containing 0.03 mg/kg UFP-101. Following the injections, orofacial pain levels were assessed through directed face grooming (mouth wiping). Statistical analyses were performed in SPSS 17.0 (Statistical Package for the Social Sciences) and p values less than 0.05 were considered as statistically significant. Results: Orofacial pain levels were significantly higher in the force group than in the control group. Orofacial pain levels differed significantly between the force group, force+saline periodontal group and force+UFP-101 periodontal group, but were similar between the control group, force+UFP-101 intraperitoneal group and force+saline intraperitoneal group. Moreover, orofacial pain levels did not differ between the force group, force+saline intraperitoneal group and force+UFP-101 intraperitoneal group. Conclusions: Periodontal, but not intraperitoneal, administration of UFP-101 could alleviate orofacial pain induced by experimental tooth movement in rats, suggesting that periodontal N/OFQ receptors participate in orofacial pain induced by experimental tooth movement.