Objective: To observe the effects of methylprednisolone(MP) on expressions of FOS and NOS in the paraventricular nucleus (PVN) of the hypothalamusfollowing the acute spinal cord injury(SCI). Methods:The total of 36 adult SD rats were randomly divided into 3 groups: control group, SCI group and MP treatment group. The rats in SCI and MP treatment groups were received the spinal transection at the fourth thoracic segment(T4). MP treated rats were given intravenous injection MP(30 mg/kg) for once, or once daily for one week or four weeks, respectively. FOS and/or NOS positive neurons were mapped in the PVN using NADPH-d histochemistry combined with Fos immunohistochemistry. Results:Compared with control group, the numbers of FOS positive neurons and NOS positive neurons were increased in the PVN, which were decreased following MP treatment for one week or four weeks. Conclusion:MP may have the protective effects on neurons in the PVN following the SCI.