The effect of fluorocitrate on CFA-induced orofacial hyperalgesia. CFA was injected into the right masseter muscle (Masseter-CFA, A-D) or into the right cutaneous site overlying masseter muscle (S-CFA, E, F). Masseter inflammation was associated with bilateral hyperalgesia and only ipsilateral hyperalgesia was seen after cutaneous inflammation, tested at 24 h after inflammation immediately before the injection of the drug. Fluorocitrate (FC, 1.0 μg) was injected into the Vi/Vc (A, B) or caudal Vc (C-F) in a volume of 500 nl after establishing behavioral hyperalgesia at 24 h after CFA. The attenuation of hyperalgesia was observed as a significant increase in EF50s. Injection of fluorocitrate into the Vi/Vc transition zone attenuated hyperalgesia bilaterally after masseter CFA (A, B). Injection of fluorocitrate into the caudal Vc only attenuated masseter hyperalgesia on the ipsilateral site (C) and without an effect on contralateral hyperalgesia (D), compared to saline (vehicle)-injected rats. Injection of fluorocitrate into the caudal Vc attenuated cutaneous hyperalgesia (E) and without an effect on the contralateral side (F). Injection of fluorocitrate into either Vi/Vc or Vc did not produce an effect in non-inflamed (Naive) rats. Asterisks denote significant differences between the post-CFA (time 0) and after 1.0 ng IL-10 microinjection (*, p < 0.05; **, p < 0.01). (ANOVA with repeated-measures and post hoc tests).