Background: Neuropathic pain is a type of chronic pain resulting from injury to the peripheral or central nervous system. Moreover, lithium is the main medication used to treat bipolar (manic-depression) disorder and some recent studies have also confirmed the neuroprotective effects of lithium. Considering the most common cause of neuropathic pain, nerve injury, the present study was designed to evaluate the effect of lithium on neuropathic pain induced by partial ligation of sciatic nerve in rat.

Materials and Methods: This experimental study was conducted on 40 adult male rats. Neuropathic pain was induced by a partial sciatic nerve ligation model and animals were randomly divided into five groups: a control group that underwent the surgical procedure without sciatic nerve ligation and four experimental groups which received normal saline and different doses of lithium (5, 10 and 15 mg/kg, i.p.). Heat hyperalgesia, mechanical and cold allodynia were assessed at 3, 5, 7, 10 and 14 days after surgery.

Results: According to the results, lithium (5, 10 and 15 mg/kg) significantly reduced heat hyperalgesia and cold allodynia induced by partial sciatic nerve ligation (P<0.01), while it reduced mechanical allodynia only at high doses (10 and 15 mg/kg).

Conclusion: Lithium has an analgesic effect on neuropathic pain induced by partial ligation of sciatic nerve in rat. Further investigations would be needed to confirm the analgesic effect of lithium and its mechanisms of action in neuropathic pain.