Figure 2.

Effect of s.c. administration of opioid receptor antagonists on the peripheral antinociception produced by PnPP‐19. (A) Non‐specific opioid receptor antagonist naloxone (50, 100, 200 μg per paw), (B) μ‐opioid receptor antagonist clocinnamox (40 and 80 μg per paw), (C) δ‐opioid receptor antagonist naltrindole (60 and 120 μg per paw) and (D) κ opioid receptor antagonist nor‐binaltorphimine (100 μg per paw) were administered 30 min before the injection of PnPP‐19 (10 μg per paw). PnPP‐19 was administered at 2 h and 55 min after local administration of PGE₂ (2 μg per paw). The response was measured by the paw‐pressure test. Data are shown as the mean ± SEM (n = 4); *P < 0.05 compared with PGE₂ + Veh + Veh and ^# P < 0.05 compared with PGE₂ + Veh + PnPP‐19 (10 μg per paw) (ANOVA + Bonferroni's test). Veh: saline; Pep: PnPP‐19.