Figure 1.
Effect of a SOD mimetic, MnTBAP, on capsaicin-induced hyperalgesia in response to vF (#3.61). a, Sites of capsaicin injection and behavioral testing in the mouse hind foot. For capsaicin injection, a 30-gauge needle was inserted at the heel of the foot (X) and advanced to the injection site (I), and capsaicin (25 μg in 5 μl of vehicle) was injected intradermally. Foot withdrawal frequencies in response to von Frey stimuli were measured at site P for primary hyperalgesia and at site S for secondary hyperalgesia. b, c, Posttreatment effect; d, e, pretreatment effect. b–e,The mean ± SEM (n = 6/group) of primary (b, d) and secondary hyperalgesia (c, e) are plotted against the postcapsaicin treatment time. MnTBAP [or vehicle saline (Sal)] was injected systemically (intraperitoneally) 1.5 h after or 0.5 h before (indicated by downward arrows) capsaicin injection (indicated by upward arrowheads) for posttreatments or pretreatments, respectively. MnTBAP reduced capsaicin-induced secondary hyperalgesia in a dose-dependent manner but not primary hyperalgesia. *Values significantly different from corresponding values of the vehicle-treated group at p ≤ 0.05, by Duncan's post hoc test after two-way repeated ANOVA. The data indicate that removal of superoxides exogenously supplemented by a SOD mimetic, reduces capsaicin induced secondary hyperalgesia. MnTBAP(Mn-T) doses: 2, 5, or 10 mg/kg body weight.