Figure 2. (Top) Time-dependent changes in skin twitch after epidural injection of 5 mg/3 ml morphine in saline, 10 mg/3 ml C0401, 30 mg/3 ml C0401, or blank DepoFoam (3 ml). Values are presented as the mean +/- SD of the respective response latencies. N = five animals at each treatment. The rank ordering of the absolute peak increase in skin-twitch response latency was 30 mg/3 ml C0401 = 10 mg/3 ml C0401 = 5 mg/3 ml morphine in saline > blank = 0. The rank ordering of the area under the time effect curve for significant antinociception was 30 mg/3 ml C0401 > 10 mg/3 ml C0401 = 5 mg/3 ml morphine in saline > blank = 0 (one-way repeated measures analysis of variance, P < 0.05 and post hoc Bonferroni tests). (Bottom) Histograms present the time of onset (left) and offset (right), respectively, of antinociceptive effects of epidurally administered blank DepoFoam (B); epidural morphine (5 mg in saline; MS-5), 10 mg/3 ml C0401 (C-10) or 30 mg/3 ml C0401 (C-30). The ordering of the time to onset was 10 mg/3 ml C0401 = 30 mg/3 ml C0401 > 5 mg/3 ml morphine in saline (one-way repeated measures analysis of variance, P < 0.05 and post hoc Bonferroni tests). The ordering of the time to offset was 30 mg/3 ml C0401 = 10 mg/3 ml C0401 = 5 mg/3 ml morphine in saline (one-way repeated measures analysis of variance, P < 0.05 and post hoc Bonferroni tests). Blank DepoFoam injections had no significant effect on nociceptive thresholds.