Anti-Nociceptive Activity of Aqueous Licorice Root Extract on Neuropathic Pain and Its Effect on Some Selected Biochemical Parameters in Male Wistar Rats

Licorice (Glycyrrhiza glabra) is a traditional medicinal, sweet and soothing herb known for its antiinflammatory effect in painful conditions. Neuropathic pain is associated with certain set of symptoms, increased drug prescriptions and regular visits to health care providers. In the present study, we examined the effect of licorice on chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain. Neuropathic pain was induced by CCI of sciatic nerve in 6-week-old male albino rats for 3weeks. Paw withdrawal thresholds were assessed on day 3, 7, 14 and 21 using von Frey test after which serum levels of cortisol, brain lactate dehydrogenase (LDH) and brain nitric oxide (BNO) were evaluated using ELISA kit.Groups treated with low dose licorice post-surgery treated (LDL), high dose licorice post-surgery treated (HDL), low dose licorice pre-surgery treated (LDLp), high dose licorice pre-surgery treated (HDLp) and imipramine demonstrated significant increase in change of paw withdrawal threshold compared with ligated control. Serum levels of Cortisol, brain LDH and BNO were significantly reduced in HDL, LDLp and HDLp treated groups when compared with ligated control. Our result shows that licorice extract demonstrates anti-nociceptive activity by reducing the serum level of cortisol, brain LDH and BNO and the effect is dose and duration dependent.