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BACKGROUND: Central nervous system axons regenerate poorly following neonatal hypoxic-ischemic brain damage (HIBD), partly due to inhibitors, such as Nogo-A. Very few studies have addressed the regulation of Nogo-A in neonatal rats following HIBD. However, numerous studies have shown that ephedrine accelerates neuronal remodeling and promotes recovery of neural function in neonatal rats following HIBD. OBJECTIVE: To investigate the effects of ephedrine on expression of Nogo-A and synaptophysin in brain tissues of neonatal rats following HIBD. DESIGN, TIME AND SETTING: A completely randomized, controlled study was performed at the Immunohistochemistry Laboratory of the Research Institute of Pediatrics, Children's Hospital of Chongqing Medical University from August 2008 to March 2009. MATERIALS: Ephedrine hydrochloride (Chifeng Pharmaceutical Group, China), rabbit anti-Nogo-A polyclonal antibody (Abcam, UK), and rabbit anti-synaptophysin polyclonal antibody (Lab Vision, USA) were used in this study.METHODS: A total of 96 healthy, neonatal, Sprague Dawley rats were randomly assigned to three groups (n = 32): sham operation, HIBD, and ephedrine. The HIBD model was established by permanent occlusion of the left common carotid artery, followed by 2 hours of hypoxia (8% oxygen and 92% nitrogen). In the sham operation group, the left common carotid artery was exposed, but was not ligated or subjected to hypoxia. Rats in the ephedrine group were intraperitoneally injected with ephedrine immediately following HIBD, with 1.5 mg/kg each time. Rats in the sham operation and HIBD groups were injected with an equal volume of saline. All neonatal rats were treated once daily for 7 days. MAIN OUTCOME MEASURES: Histopathological damage to the cortex and hippocampus was determined by hematoxylin-eosin staining. Expression of Nogo-A and synaptophysin was detected using immunohistochemical staining.RESULTS: Neuronal degeneration and edema were observed in the hypoxic-ischemic cortex and hippocampus by hematoxylin-eosin staining. Compared with the sham operation group, the levels of Nogo-A significantly increased in the HIBD group at various time points (P < 0.01). Nogo-A expression was significantly reduced in the ephedrine group compared with the HIBD group (P < 0.01). Synaptophysin expression was significantly decreased in the hypoxic-ischemic cortex, compared with the sham operation group (P < 0.01). Synaptophysin levels were significantly increased in the ephedrine group, compared with the HIBD group (P < 0.01). CONCLUSION: Altered Nogo-A expression was associated with inversely altered synaptophysin expression. The use of ephedrine normalized expression levels of Nogo-A and synaptophysin following HIBD.