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. Author manuscript; available in PMC: 2010 Oct 1.
Published in final edited form as: Pain. 2009 Jul 30;145(3):332–340. doi: 10.1016/j.pain.2009.06.035

Fig. 5.

Fig. 5

Effect of systemic naltrexone (NTX; a non-specific opioid receptor antagonist) on capsaicin-induced primary and secondary hyperalgesia. A and B show the effect of pretreatment of systemic NTX (i.p., 10 mg/kg) on EA-induced antihyperalgesic effect on the primary (A) and secondary (B) hyperalgesia. Naltrexone (or saline) was injected intraperitoneally (i.p.) 10 min after beginning of EA. C and D show the effect of systemic NTX (i.p., 10 mg/kg) injected during the maintenance of EA-induced antihyperalgesia on the primary (C) and secondary (D) hyperalgesia. Naltrexone (or saline) was injected intraperitoneally (i.p.) immediately after behavior measurement at 0.5 hr post EA. Data are expressed as means ± SEM. Number of animals - A and B: 6 in NTX and 7 in Saline groups; C and D: 6 in NTX and 6 in Saline groups. Data were analyzed by two-way repeated measure ANOVA, followed by the Holm-Sidak post hoc test. *, a value significantly (p<0.05) different from the corresponding value in the saline control group.