• Satoshi Fuseya, Katsumi Yamamoto, Hitoshi Minemura, Satoshi Yamaori, Tomoyuki Kawamata, and Mikito Kawamata.
• From the Department of Anesthesiology and Resuscitology, Shinshu University School of Medicine, Matsumoto City, Nagano, Japan (S.F., K.Y., H.M., T.K., M.K.); and Department of Pharmacy, Shinshu University Hospital, Matsumoto City, Nagano, Japan (S.Y.).
• Anesthesiology. 2016 Jul 1; 125 (1): 204-18.

BackgroundThe aim of this study was to determine whether systemic administration of QX-314 reduces bone cancer pain through selective inhibition of transient receptor potential vanilloid subfamily 1 (TRPV1)-expressing afferents.MethodsA mouse model of bone cancer pain was used. The authors examined the effects of bolus (0.01 to 3 mg/kg, n = 6 to 10) and continuous (5 mg kg h, n = 5) administration of QX-314 on both bone cancer pain-related behaviors and phosphorylated cyclic adenosine monophosphate response element-binding protein expression in dorsal root ganglion neurons (n = 3 or 6) and the effects of ablation of TRPV1-expressing afferents on bone cancer pain-related behaviors (n = 10).ResultsThe numbers of flinches indicative of ongoing pain in QX-314-treated mice were smaller than those in vehicle-treated mice at 10 min (3 mg/kg, 4 ± 3; 1 mg/kg, 5 ± 3 vs. 12 ± 3; P < 0.001; n = 8 to 9), 24 h (3 ± 2 vs. 13 ± 3, P < 0.001), and 48 h (4 ± 1 vs. 12 ± 2, P < 0.001; n = 5 in each group) after QX-314 administration, but impaired limb use, weight-bearing including that examined by the CatWalk system, and rotarod performance indicative of movement-evoked pain were comparable. QX-314 selectively inhibited the increase in phosphorylated cyclic adenosine monophosphate response element-binding protein expression in TRPV1-positive, but not in TRPV1-negative, dorsal root ganglion neurons compared to that in the case of vehicle administration (32.2 ± 3.0% vs. 52.6 ± 5.9%, P < 0.001; n = 6 in each group). Ablation of TRPV1-expressing afferents mimicked the effects of QX-314.ConclusionThis study showed that systemic administration of QX-314 in mice inhibits some behavioral aspects of bone cancer pain through selective inhibition of TRPV1-expressing afferents without coadministration of TRPV1 agonists.

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