Fig. 2

Partial antagonism induced by intracerebroventricular administration of a naloxone, b clocinnamox, c naltrindole or d AM251 in the central antinociception induced by PnPP-19. Naloxone (Nal; 2.5 and 5 μg), clocinnamox (Clo; 2 and 4 μg), naltrindole (NTD; 6 and 12 μg) or AM251 (2 and 4 μg) was administered 1 min prior to PnPP-19 injection (1 μg). These antagonists did not significantly modify the nociceptive threshold in the control group. Each line represents the mean ± SEM for four mice per group. *Significant difference compared to the control group (ANOVA + Bonferroni’s test). Sal: saline (0.5% of Evans Blue); Veh: vehicle (20% DMSO in saline 0.5% of Evans Blue)