Figure 2. Effects of σ₁ agonists on acute nociceptive behaviors induced by the intraplantar (i.pl.) administration of capsaicin in wild-type mice.

The results show the duration of licking or biting of the paw injected with capsaicin (0.125 μg) or its vehicle (VH, DMSO 1%). Behavioral responses were recorded at intervals of 0–5 min (A) and 5–10 min (B) after the i.pl. administration of capsaicin or its vehicle. PRE-084 (PRE), (+)-pentazocine (PTZ), carbetapentane (CBP) or their solvent (saline) were subcutaneously (s.c.) administered 30 min before the i.pl. injection. (A and B) Each bar and vertical line represents the mean ± SEM of the values obtained in 8–10 animals. Statistically significant differences between the values obtained in mice treated with capsaicin or its solvent: **p < 0.01. There were no statistically significant differences between the values obtained in capsaicin-treated animals administered with the σ₁ agonists or their solvent (two-way ANOVA).