Preclinical evaluation of antinociceptive effect of withania somnifera (ashwagandha) in diabetic peripheral neuropathic rat models

The present study was designed to investigate the antinociceptive effect of root extract of Withania. somnifera in Streptozotocin (STZ) induced diabetic peripheral neuropathic rat models. Forced swim test was carried out to determine the antidepressant activity. The interference of antidepressant agents with motor activity of rats was determined by openfeild test. Diabetes was induced by a single i.p. injection of 50 mg/kg streptozotocin. Tail immersion test (Hot & cold water) and formalin test were performed to determine the extent of neuropathic pain in diabetic rats. Imipramine (10.5mg/kg), flouxetine (14.5mg/kg), Quercetin (10mg/kg) and W. somnifera (100mg/kg) was administered orally for 21 consecutive days starting after 4^th week in STZ induced diabetic rats. Thiobarbituric acid reactive substance (TBARS), superoxide dismutase (SOD), and Catalase in serum were also performed to access the oxidative stress. Mode of action of W. somnifera was determined by administering naloxone (2 mg/kg) prior to its administration. Chronic treatment with W. somnifera for 3 weeks starting after 4^th week in STZ induced diabetic rat's attenuated hyperalgesia. It also ameliorated diabetic induced raised level of TBARS, and decreased level of SOD and Catalase. Antinociceptive activity of W. somnifera was reversed by prior administration of naloxone. It was concluded that antidepressant and antioxidant effect may be responsible for observed antinociceptive effect of W. somnifera in STZ induced diabetic peripheral neuropathic rat models.