Uterine mustard oil (MO) administration provokes painful colonic contractions and spinal NR2B phosphorylation. (A) When compared with the preinjection control, corn oil (CO; 0.2 ml; indicated by an arrow at the bottom) administration into the uterine horn neither induced colonic motility in the intracolonic pressure (ICP) nor triggered firing in the electromyogram (EMG) tracings. (B) Intrauterine MO (0.1%, 0.2 ml; indicated by an arrow at the bottom) dispensing dramatically provoked rhythmic colonic contractions with synchronized burst EMG discharges. (C and D) Intrauterine administration of MO, but not CO, significantly increased the contraction count in the ICP curve and the area of integrated EMG (iEMG) compared with the preinjection control (**P < 0.01, vs. control, both n = 7). (E) When compared with the preinjection control, MO administration into the uterine horn increased the band intensity of phosphorylated NR2B in a time-dependent manner (normalized by the β-actin) in dorsal horn samples (L6-S1) at 10, 30, and 60 min after administration (*P < 0.05, ** P < 0.01, vs. control, n = 7). However, this treatment failed to affect the band intensity of total NR2B (normalized by the β-actin; P > 0.05, vs. control, n = 7) or β-actin (P > 0.05, vs. control, n = 7). (F) When compared with the preinjection control, uterine MO injections, but not CO injections, significantly increased the optical density of the Evans Blue extravasation in the uterus (**P < 0.01, vs. control, both n = 7). There was no difference in the optical density of the Evans Blue extravasation in the descending colon between the preinjection control and uterine CO or MO injections (both P > 0.05 vs. control, n = 7). pNR2B = phosphorylated NR2B; tNR2B = total NR2B.