Fig. 3.

Ipsilateral but not contralateral administration of herkinorin attenuates the formalin-induced flinch response. A. Timecourse of formalin-induced flinching behavior for groups of rats treated with vehicle, morphine (10 mg/kg), or herkinorin (10 mg/kg) at the ipsilateral or contralateral paw. Ipsilateral injections analyzed in figure 1 and shown here for comparison. Morphine is active on both the contralateral and ipsilateral sides while herkinorin is only active at the site of injection. Data are presented as mean ± SEM and are analyzed via two-way ANOVA. B. First and second phase analysis. Ipsilateral injections of morphine or herkinorin significantly block the flinch response at 10 mg/kg while only contralateral morphine injection produced antinociception (First phase (left): vs. vehicle, **p<0.01, ***p<0.001; Second phase (right): vs. vehicle: ***p<0.0001, n=4-7). Data are presented as the mean ± SEM of the sum of flinches in each phase and are analyzed by Student’s t test.