Figure 2 | Scientific Reports

Figure 2

From: A low pKa ligand inhibits cancer-associated pain in mice by activating peripheral mu-opioid receptors

Figure 2

Effects of i.v. fentanyl and NFEPP on heat hyperalgesia in mice inoculated with killed B16-F10 cells. (A) Dose–response effects of fentanyl (30–100 nmol/kg) and NFEPP (100–1000 nmol/kg) on ipsilateral paw withdrawal latencies (n = 5 per group). *P < 0.05, **P < 0.01 compared to solvent (0 nmol/kg)-treated mice, one-way ANOVA and Dunnett’s t test. (B) Systemic naloxone (NLX; 1 mg/kg s.c. at the neck) but not the local injection of naloxone-methiodide (NLX-MET; 1 µg s.c. in the calf) into the inoculated limb inhibited the antinociceptive effect of fentanyl (F) and NFEPP (NF) (n = 7 in F + NLX-MET group, n = 5 per group for other treatments). **P < 0.01 compared to the corresponding paw of the respective solvent (SOL)-treated mice, two-way ANOVA and Tukey’s test. All data are means ± SEM. For clarity, in the graphs a maximal number of two symbols of significancy are represented (the exact values are stated in the results section).

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