FIGURE 6.

Effect of low-dose naloxone and ICI 118,551 on thermal hyperalgesia induced by compounds (a) 5, (b) 10, (c) 11 and (d) 25 in naïve adult C57BL/6 mice. The temporal changes in the ΔTWL values induced by s.c. administration of ~ED₇₅ dose of (a) compound 5 (n = 8, 7 and 7 for vehicle, naloxone and ICI 118,551, respectively) was significantly reversed by i.p. administration of low dose naloxone (1 mgkg⁻¹), but not ICI 118,551 (5 mgkg⁻¹). In contrast, thermal hyperalgesia induced by s.c. administration of ~ED₇₅ doses of compounds (b) 10, (c) 11 and (d) 25 were significantly attenuated by i.p. administration of ICI 118,551 (5 mgkg⁻¹; n = 7 per test compound), but not the non-selective opioid antagonist, naloxone (1 mgkg⁻¹; n = 7 per test compound), relative to vehicle (n = 7 per test compound). Data presented as mean ± SEM. *P < 0.05, significantly different, ns, non-significantly different, as indicated; two-way ANOVA with post hoc Bonferroni test