Fig. 4

Effect of σ1R or σ2R deletion on analgesia induced by opioids and nonopioid compounds. Analgesic compounds were icv injected, and the time course of analgesia was evaluated in σ2R^−/− (KO; left panel), σ1R^−/− mice (KO; right panel) and corresponding wild-type mice (WT). Analgesia was determined by the warm water (52 °C) tail-flick test at the indicated intervals postinjection. The values are mean ± SEM of groups of 6–8 mice. * Indicates significantly different compared to WT mice; all data were analyzed by pairwise Holm-Sidak multiple comparison tests following ANOVA; p < 0.05