The analgesic effect of koumine was reversed in sciatic nerve chronic constriction injury rats by intrathecal treatment with medroxyprogesterone acetate. Medroxyprogesterone acetate (MPA) or dimethyl sulfoxide (DMSO, vehicle) was administered via an intrathecal catheter 10 days after sciatic nerve chronic constriction injury (CCI) surgery. After 30 min, koumine (7 mg kg−1 bw) or normal saline (NS) was administered by subcutaneous (s.c.) injection. The mechanical withdrawal threshold (MWT) of the hind paws was measured 1 h after completion of the drug or vehicle administration. The data are presented as the mean ± SEM (n = 6 per group) and were analyzed by one-way ANOVA followed by Bonferroni post hoc test at each time point. *P < 0.05 vs. the DMSO + NS group; #
P < 0.05 vs. the DMSO + koumine group.