The Effect of the Flavonoid Quercetin on Pain Sensation in Diabetic Rats

Hyperalgesia is considered as one of the marked signs of subchronic diabetes mellitus in patients that could affect their lifestyle. This study was designed to investigate the anti-nociceptive effect of chronic administration of quercetin in streptozotocin (STZ)-diabetic rats using formalin and hot tail immersion tests. Rats were divided into control, control or diabetic groups receiving sodium salicylate, untreated diabetic, and quercetin-treated control and diabetic groups. The treatment groups received i.p. administration of quercetin at a dose of 10 mg/kg for 6 weeks. Finally, hyperalgesia were assessed using standard formalin and hot tail immersion tests. Meanwhile, some markers of oxidative stress were also measured in brain tissue. Quercetin or SS treatment of diabetic rats significantly reduced pain score in chronic phase of formalin test (p<0.05). Regarding hot tail immersion test, diabetic rats showed a significant reduction in tail flick latency as compared to control ones (p<0.05) and quercetin treatment of diabetic rats did significantly increase this latency relative to untreated diabetics (p<0.05). Quercetin treatment of diabetic rats also significantly decreased brain level of malondialdehyde (MDA) (p<0.05) and nitrite (p<0.05) and slightly increased activity of superoxide dismutase (SOD) relative to diabetics. Taken together, chronic administration of quercetin could attenuate nociceptive score in chronic phase of formalin test in streptozotocin-diabetic rats and could also increase threshold of thermal nociception.