Background: Newly developed antidepressants like serotonin norepinephrine reuptake inhibitors (SNRI) are tried to treat many chronic pain conditions. We probed if there is any antiallodynic effects of milnacipran, one of SNRI, in neuropathic pain using the rat spinal nerve ligation (SNL) model. Methods: Female Sprague-Dawley rats weighing 200∼250 g were used for this study. Under general anesthesia, the SNL model was made by ligating the 5th and 6th lumbar spinal nerve. Intrathecal catheter (PE-10) was inserted into subarachnoid space and 0.1, 0.3, 1.0, 3.0 and 10.0μg of milnacipran was delivered and the antiallodynic effect was measured by von Frey hair. To study the effect of chronic administration of milnacipran beforehand, for the development of neuropathic pain, different dose (10 and 20 mg/kg) of subcutaneous milnacipran was injected twice a day for 2 weeks before SNL operation, and the development of allodynia was evaluated for 4 weeks. Result: Intrathecal milnacipran exerted the dose-dependent antiallodynic effect in spinal nerve ligated model. But chronic systemic adminstration of milnacipran in advance before neuropathic induction did not influence the development of allodynia in SNL model. Conclusions: Intrathecal milnacipran reduced the allodynia in rat SNL model. But the chronic subcutaneous injection beforehand did not change the development of allodynia after spinal nerve ligation model in rats.

KeywordsIntrathecal milnacipran, Rat neuropathic pain, Rat