Fig. 4.

Herkinorin produces antinociception following chronic herkinorin treatment. Herkinorin or vehicle was given subcutaneously (i.pl.) for 4 days and testing was conducted on day 5. A. Timecourse of formalin-induced flinching behavior for groups of rats treated with vehicle or herkinorin. Herkinorin was antinociceptive prior to and following chronic treatment. Repeated vehicle treatments had no effect. Herkinorin had slightly decreased efficacy following the chronic treatment. Data are expressed as the mean ± SEM and are analyzed by two-way ANOVA. B. First and second phase analysis. Herkinorin maintained antinociceptive activity in both phases of the formalin test following chronic administration although the effects were slightly diminished following the chronic treatment regimen (First phase (left): vs. vehicle of the same day: *p<0.05, **p<0.01; vs. herkinorin day 1: ^#p<0.05; Second phase (right): vs. vehicle of the same day: ***p<0.0001; vs. herkinorin day 1: ^##p<0.01, 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.