Effects of tin protoporphyrin IX (SnPP) treatment on the antiallodynic and antihyperalgesic responses to morphine, [d-Pen(2),d-Pen(5)]-enkephalin (DPDPE) or (2-methyl-1-propyl-1H-indol-3-yl)-1-naphthalenylmethanone (JWH-015). Local (A, B, C) and systemic (D, E, F) mechanical antiallodynic (A, D), thermal antihyperlagesic, (B, E) and thermal antiallodynic (C, F) effects of the subplantar or systemic administration of morphine (100 µg or 5 mg/kg), DPDPE (25 μg or 0.5 mg/kg), or JWH-015 (5 μg or 0.15 mg/kg) combined with SnPP (290 μg or 10 mg/kg) at 10 days after surgery are shown. The effects of the subplantar or subcutaneous administration of morphine, DPDPE, JWH-015, SnPP, or vehicle alone are also represented. Data are expressed as mean values of the maximal possible effect (%) for mechanical allodynia and thermal hyperalgesia and as inhibition (%) for thermal allodynia ± SEM (6 animals per group). For each behavioral test, * denotes significant differences versus group treated with vehicle (P < 0.05, one-way ANOVA followed by Student Newman–Keuls test), + denotes significant differences versus group treated with SnPP plus vehicle (P < 0.05, one-way ANOVA followed by the Student Newman–Keuls test), and # denotes significant differences versus group treated with morphine plus vehicle (P < 0.05, one-way ANOVA followed by the Student Newman–Keuls test).