Dynorphin A content is similar after SNL or Sham surgery in the ipsilateral dorsal quadrant of the lumbar spinal cord of postpartum rats (PP) analyzed by enzyme immune-assay. Data are expressed as Mean ± SD; n=7 in each group of postpartum (PP) rats and n=14 in each group of control (virgin females) rats. Groups were analysis by Two way ANOVA, p (Group)=0.004, p (Surgery)=0.228, p (Group x Surgery)=0.224. Bonferroni’s Multiple Comparison Test, *p <0.05 compared to control SNL, #p <0.05 compared to control Sham.