Effect of alcoholic extract of Iranian red onion on diabetic neuropathic pain in streptozotocin-diabetic rats

Introduction: Neuropathic pain is one of the common complications of diabetes mellitus which is caused by impairment in nerve conductivity. The role of flavonoid and polyphenol compounds in treatment of neuropathic pain has been revealed, and extract of onion contains significant amounts of these compounds. The aim of this study was to investigate the effect of alcoholic extract of onion on diabetic neuropathic pain in streptozotocin-diabetic rats. Methods: In this experimental study, 40 male Wistar rats were divided into 5 groups: normal control, diabetic control and groups receiving alcoholic extract of onion (125, 250 and 500 mg/kg/day). After injection of streptozotocin (55 mg/kg), the extract was administered for 3 weeks. At days 0, 7, 14 and 21 after injection of streptozotocin, assessment of neuropathic pain was performed by thermal allodynia, mechanical allodynia, hyperalgesia and formalin test. Results: Behavioral responses to thermal and mechanical stimuli in diabetic control rats showed significant reduction (P<0.05). Oral administration of alcoholic extract of onion at doses of 125 and 250 led to improvement in diabetic neuropathic pain in all 4 tests. However, dose of 500 mg didn’t improve neuropathic pain. Conclusion: Oral administration of alcoholic extract of Iranian red onion improves diabetic neuropathic pain in rats.