BACKGROUND: Ligustrazine can reduce the production of free radicals and the content of malonaldehyde, and improve the enzymatic activity of adenosine-triphosphate in cerebral anoxia. It also can increase the expression of heat shock protein-70 and Bcl-2, thus alleviating brain tissue injury caused by cerebral ischemia/reperfusion. This study aimed to address the question of whether ligustrazine can protect the membrane structure of neurons.OBJECTIVE: To establish rat models of cerebral ischemia/reperfusion, observe the membrane structure and main organelles of neurons with electron microscope after ligustrazine intervention, and to analyze the dose-dependent effects of ligustrazine on neuronal changes.DESIGN: Arandomized controlled study.SETTING: Department of Anatomy Research and Electron Microscopy, Hebei North University. MATERIALS: Forty Wistar rats of SPS grade, weighing 180–250 g and equal proportion of female and male, were provided by Hebei Medical University Animal Center (No. 060126). The ligustrazine injection (40 g/L, No. 05012) was produced by Beijing Yongkang Yaoye. LKB4 Ultramicrotome was purchased from LKB Company in Sweden. JEM100CXII electron microscope was purchased from JEOL in Japan.METHODS: The experiment was performed in the Laboratory of the Department of Anatomy and Electron Microscopy, Hebei North University from June to August 2006. ① Wistar rats were allowed to adapt for 3 days, and were then randomly divided into four groups, according to the numeration table method: normal group, model group, low-dose ligustrazine group, and high-dose ligustrazine group. There were 10 rats in each group. ②Rats in the model group, low-dose ligustrazine group, and high-dose ligustrazine group un-derwent cerebral ischemia/reperfusion model, according to Bannisters method. The carotid artery was opened for reperfusion after 90 minutes of cerebral ischemia. Samples were collected from the cerebral cor-tex after 24 hours. Animals from the ligustrazine low-dose group and ligustrazine high-dose group received ligustrazine injections, 50 mg/kg and 100 mg/kg, respectively. Samples were collected at the same time as the model group.MAIN OUTCOME MEASURES: Alterations of the neuronal ultrastructure and main organelles were ob-served by electron microscopy.RESULTS: Forty Wistar rats were included in the final analysis. Plentiful ribosome and rough endoplasmic reticulum existed in the cytoplasm of cortical neurons in the normal group. Edema existed in the nucleus and cytoplasm of neurons in the model group. The cell membrane was damaged, resulting in the external erup-tion of certain cellular organelles. In the low-dose ligustrazine group, neuronal swelling was decreased in the cytoplasm, whereas cellular organelles were relatively increased. However, the mitochondria remained swollen. The double layer structure disappeared in parts of the mitochondrial membrane. The caryotheca was still broken, and neuronal damage was significantly decreased in the high-dose ligustrazine group. In ad-dition, cytoplasmic swelling was reduced andmost part of caryotheca was complete. Fragmentation of the cellular membrane was not detected. Mitochondrial cristae and the lysosome could also be detected. The number of rough endoplasmic reticulum and free ribosomes was increased, and the structure of great part of caryotheca was clear. In addition, the number of nuclear pore was increased. However, the nuclear hetero-chromatin was relatively reduced.CONCLUSION: In the rat, the protective effects of ligustrazine were significant on neuronal membrane structures and main organelles after cerebral ischemia/reperfusion. There was a dose-dependent effect be-tween neuronal changes and Ligustrazine.