Neuroprotective Effects of Licorice Extracts in Tibial and Sural Transection Induced Neuropathic Pain in Rats

Background: Neuropathic pain (NP) is the worst of tortures, a nerve wound may experience as a result of nerve damage or complication of diabetes/HIV/cancer. There are no defined guidelines for treatment. Available treatments have various side effects. Glycyrrhiza glabra (Licorice) has not been explored scientifically with respect to NP. Hence there is a dire need to develop treatment for NP which will be safe, effective and can be taken for prolonged time. The present study is to evaluate effects of licorice extracts in Tibial and Sural Transection (TST) induced neuropathic pain in rats. Materials and Methods: Extracts prepared from crude drug were tested for antioxidant activity. NP was induced by TST surgery method. After induction of NP, it leads to chemical and heat evoked hyperalgesia, cold and mechanical allodynia. Rats were divided into eight groups, Control (Treated with Na-CMC), Standard (Treated with Pregabalin), Test (Treated with three licorice extracts), Sham operated and Normal (Without surgery). Rats were treated with extracts and standard for 21 days. At the end of 21 days’ rats were sacrificed and tested for biochemical parameters. At the end of study biochemical parameters; superoxide generation, malondialdehyde (MDA) and TNF-α were evaluated. Results: Rats treated with licorice extracts showed improvement all the pain related symptoms and tibial functional index. Treated rats also showed significant improvement in superoxide ions and MDA supporting their antinociceptive and antioxidant activities. Conclusion: Licorice extracts have shown significant decrease in pain symptoms in TST induced NP in rats. This effect may be attributed to anti-inflammatory, antioxidant and neuroprotective properties of licorice. Hence licorice extracts can be potential candidates for treatment of NP.