Effects of combining methylprednisolone with magnesium sulfate on neuropathic pain and functional recovery following spinal cord injury in male rats.

Methylprednisolone (MP) has been widely used as a standard therapeutic agent for the treatment of spinal cord injury (SCI). Because of its controversial useful effects, the combination of MP and other pharmacological agents to enhance neuroprotective effects is desirable. Magnesium sulfate (MgSO4) has been shown to have neuroprotective and antihyperalgesic effects. In the present study, we sought to determine the effect of combining MP and MgSO4, on neuropathic pain and functional recovery following spinal cord injury (SCI) in male rats. A total of 48 adult male rats (weight 300-350 g) were used. After laminectomy, complete SCI was achieved by compression of the spinal cord for one minute with aneurysm clips. Single doses of Magnesium sulfate (MgSO4), (600 mg/kg), Methylprednisolone (MP), (30 mg/kg) or combining MgSO4 and MP were injected intraperitoneally. Prior to surgery and during four weeks of study Tail flick latency (TFL) and BBB (Basso-Beattie-Bresnahan) score and the acetone drop test were evaluated. In mean values of BBB score, a significant difference was observed in SCI+veh compared with other groups (P<0.05). Mean TFL also was significantly higher in SCI+veh compared with other groups (P<0.05). Mean acetone drop test score and weight were significantly different in MgSO4, MP and combining MgSO4 and MP  treated groups compared with SCI+veh group (P<0.05). These findings revealed that MP, MgSO4 and combining MgSO4 and MP treatment can attenuate neuropathic pains following SCI in rats include: thermal hyperalgesia and cold allodynia. They also can yield better improvement in motor function and decrease weight loss after SCI in rats compared with the control group.