The Therapeutic Effect of Vitamin C in an Animal Model of Complex Regional Pain Syndrome Produced by Prolonged Hindpaw Ischemia-Reperfusion in Rats

Abstract

Objectives: It is known that increased free radicals from oxidative stress are one of the major causes of complex regional pain syndrome (CRPS). In this study, we tested the hypothesis that vitamin C has a dose-related treatment effect in a chronic post-ischemic pain (CPIP) model. Methods: A total of 49 male rats weighing 250 to 350 g were used. The 4 treatment groups were control (no medication), group 1.0 (administration of 1 mg/day for vitamin C for 5 days), group 2.5 (administration of 2.5 mg/day vitamin C for 5 days), and group 7.5 (administration of 7.5 mg/day vitamin C for 5 days). The 50% mechanical withdrawal threshold and total blood antioxidant status (TAS) were measured before and after administration of vitamin C. Results: Twenty-eight CPIP model rats were generated from 49 rats. Seven rats were randomly allocated to each group. The 50% mechanical withdrawal threshold of group 2.5 (after the administration of vitamin C) was higher than that of the control group and group 1.0 (P < 0.05). At 1 day of the administration of vitamin C, the 50% mechanical withdrawal threshold of group 1.0 was higher than that of the control group and the blood levels of TAS in groups 2.5 and 7.5 were higher than that in control group (P < 0.05). Twelve days after the administration of vitamin C, the blood levels of TAS in groups 2.5 and 7.5 were lower than that of the control group (P < 0.05). Discussion: The administration of a proper dose of vitamin C can reduce oxidative stress, increase antioxidants, and recover the threshold for mechanical allodynia in the CPIP model.

Keywords: antioxidants; chronic post-ischemic pain model; complex regional pain syndrome; oxidative stress; vitamin C..

Figure 1

Flow chart of the study. Control group: no medication group. Group 1.0: administration of 1 mg/kg vitamin C for 5 days. Group 2.5: administration of 2.5 mg/kg vitamin C for 5 days. Group 7.5: administration of 7.5 mg/day vitamin C for 5 days.

Figure 2

Time-course changes of the 50% mechanical withdrawal threshold within each group. Control group: no medication group. Group 1.0: administration of 1 mg/kg vitamin C for 5 days. Group 2.5: administration of 2.5 mg/kg vitamin C for 5 days. Group 7.5: administration of 7.5 mg/day vitamin C for 5 days. *P < 0.05 vs. control group. Error bar: standard error.

Figure 3

Time-course changes of blood total antioxidant status within each group. Control group: no medication group. Group 1.0: administration of 1 mg/kg vitamin C for 5 days. Group 2.5: administration of 2.5 mg/kg vitamin C for 5 days. Group 7.5: administration of 7.5 mg/day vitamin C for 5 days. *: P < 0.05 vs. control group. Error bar: standard error.