Figure 1. Intra-paw injections of FLO inhibited heat nociception in naive wild-type (WT) mice and attenuated both heat and mechanical hyperalgesia after the plantar-incision.

(A) Paw withdrawal latency (PWL) to heat stimulation in naïve WT mice before and after injection of FLO (0.5 mg, 20 μL) or the vehicle (saline, 20 μL) into the dorsum of the hind paw. Ipsilateral: injected side; Contralateral: un-injected side. N=10/group. (B) The PWL ipsilateral to the side of plantar-incision was measured before and 1, 2, 4 hours after intra-paw injections of FLO (0.1 mg, 0.5 mg, 20 μL) or the vehicle in WT mice during Days 2-4 post-injury. N=7-13/group. (C) The mechanical paw withdrawal threshold (PWT) to noxious pinch applied to the side of plantar- incision was measured before and 1 hour after intra-paw injection of FLO (0.5 mg, 20 μL) or vehicle with the Randall-Selitto test during Days 2-4 post-injury. N=10-11/group. (D) Schematic of the Catwalk gait analysis (left) and the representative paw print images (right). (E) Quantification of print area and maximum contact area in Catwalk test before and 1 hour after an intra-paw injection of FLO (0.5 mg, 20 μL) or vehicle on Day 2 post-injury. The left hind paw (LH) received the incision and drug treatment, and data were normalized to the right side (RH). N=9-10/group. (F) Locomotor function and exploration were assessed in the open field test (30-min duration). The number of total, central and peripheral beam breaks were measured before and at 1 hour after an intra-paw injection of FLO (0.5 mg, 20 μL) or vehicle during Days 2-4 post-injury. N=10/group. Data are mean ± SEM. Two-way mixed model ANOVA followed by Bonferroni post hoc test. (A-C) *P<0.05, **P <0.01, ***P <0.001 versus vehicle; ^#P<0.05, ^##P<0.01, ^###P<0.001 versus baseline (A) or pre-drug (B, C). (E, F) *P<0.05, **P <0.01 versus pre-drug; ^###P<0.001, ^####P<0.0001 versus baseline. ns = not significant.