Antinociceptive Effect of Curcumin, an Effective Constituent of Turmeric, in Diabetic Rats and Evaluation of the Involvement of Lipid Peroxidation

This study was designed to investigate the antinociceptive effect of curcumin in diabetic rats by using the formalin and hot tail immersion tests. Wistar rats were divided into the following six groups: control; curcumin-treated control (50 mg/kg); diabetic; sodium salicylate (SS)-treated diabetic; and two curcumin-treated diabetic groups (10 and 50 mg/kg). Curcumin was administered seven days after streptozotocin injection for a total of five weeks. High-dose curcumin treatment of diabetic rats reduced the pain score in both acute and chronic phases of the formalin test (p<0.05). SS-treated diabetic rats had a reduction in pain score only in the chronic phase of the formalin test (p<0.05). In the hot tail immersion test, diabetic rats showed a significant reduction in tail flick latency compared to the control group (p<0.01). High-dose curcumin treated diabetic rats showed significantly increased latency relative to untreated diabetic rats (p<0.05). Diabetic rats also showed a significant increase in the tissue level of malondialdehyde (MDA; p<0.01). High-dose curcumin treated diabetic rats had a significantly reduced level of MDA (p<0.05). Chronic administration of curcumin could attenuate the nociceptive score in both the acute and chronic phases of the formalin test in a streptozotocin-induced experimental model of diabetes mellitus and increase thermal pain threshold. The beneficial effect of curcumin is partly attributed to attenuation of lipid peroxidation in the periphery.