BACKGROUND: Recent researchers report that vasospasm is caused by that, on one hand, damage of endothelial cells reduces synthesis and liberation of vessel dilator; on the other hand, defluxion of endothelial cells directly exposure vascular smooth muscles in active materials of vasoconstriction in blood. OBJECTIVE: To study whether apoptosis of cerebrovascular cells occurs in symptomatic cerebral vasospasm (CVS) rabbit models by using transmission electron microscope. DESIGN: Contrast observation. SETTINGS: The Fifth Endemic Area, the 89 Hospital of Chinese PLA; Minimally Invasive Neurosurgical Center, Tangdu Hospital, the Fourth Military Medical University of Chinese PLA. MATERIALS: A total of 24 New Zealand rabbits, of either sex, weighing 2.4-3.0 kg, of clear grade, were selected from the Experimental Animal Center of the Fourth Military Medical University of Chinese PLA. JEM-2000EX transmission electron microscope was made in Japan. METHODS: The experiment was carried out in the Laboratory of Anatomy (National Key Laboratory), the Fourth Military Medical University of Chinese PLA from April 2001 to April 2002. ① Preparation of symptomatic CVS models: Eighteen animals which were successfully modeled were randomly divided into experimental group (n =13) and control group (n =5). Animals in the experimental group were poured with blood into cavitas subarachnoidealis; while, animals in the control group were poured with the same volume of saline into cavitas subarachnoidealis. At the 5th day injection, three rabbits selected from the experimental group were anesthetized and perfused into left ventricle. And then, aorta pectoralis and caval vein were blocked by using ring clamp. Cranium was rapidly cut open to obtain cerebral basilar artery and a few of brain tissues. Both of them were fixed for 8 hours. Two rabbits selected from the control group were perfused with the same method to obtain basilar artery and brain tissues and fix. ② After fixation by using optic microscope, samples were stained with lead citrate uranyl acetate staining, observed with electron microscope and photographed. MAIN OUTCOME MEASURES: Morphological changes of cytoplasm and nucleus of vascular endothelial cells and smooth muscle cells in the two groups. RESULTS: Morphology of vascular endothelial cells in cerebral basilar artery was not changed in the control group. However, vascular endothelial cells in the experimental group showed that cytochondria were swelling; endocytoplasmic reticulum was amplified; chromatin margination was clear; nucleus was in pyknosis; endothelial cells fell down from basal membrane; cell-cell junction was broken. Changes of smooth muscle cells were similar to those of endothelial cells. Severely, it was shown that nuclear pyknosis was obvious, and this was like early apoptosis. CONCLUSION: Apoptosis of endothelial cells may occur in spasmodic vessels. BACKGROUND: Recent researchers report that vasospasm is caused by that, on one hand, damage of endothelial cells reduces synthesis and liberation of vessel dilator; on the other hand, defluxion of endothelial cells directly exposure vascular smooth muscles in active materials of vasoconstriction in blood. OBJECTIVE: To study whether apoptosis of cerebrovascular cells occurs in symptomatic cerebral vasospasm (CVS) rabbit models by using transmission electron microscope. DESIGN: Contrast observations. SETTINGS: The Fifth Endemic Area, the 89 Hospital of PLA; Minimally Invasive Neurosurgical Center, Tangdu Hospital, the Fourth Military Medical University of Chinese PLA. MATERIALS: A total of 24 New Zealand rabbits, of either sex, weighing 2.4-3.0 kg, of clear grade, were selected from the Experimental Animal Center of the Fourth Military Medical University of Chinese PLA. JEM-2000EX transmission electron microscope was made in Japan. METHODS: The experiment was carried out in the L abstratory of Anatomy (National Key Laboratory), the Fourth Military Medical University of Chinese PLA from April 2001 to April 2002. ① Preparation of symptomatic CVS ​​models: Eighteen animals which were successfully modeled were differentiated into experimental group (n = 13) and control while in animals in the control group were poured with the same volume of saline into cavitas subarachnoidealis. At the 5th day injection, three rabbits selected from the experimental group were anesthetized and perfused into left ventricle. And then, aorta pectoralis and caval vein were blocked by using ring clamp. Cranium was rapidly cut open to obtain cerebral basilar artery and a few of brain tissues. Both of them were fixed for 8 hours Two rabbits selected from the control group were perfused with the same method to obtain basilar artery and brain tissues and fix. ic microscope, samples were stained with lead citrate uranyl acetate staining, observed with electron microscope and photographed. MAIN OUTCOME MEASURES: Morphological changes of cytoplasm and nucleus of vascular endothelial cells and smooth muscle cells in the two groups. RESULTS: Morphology of vascular endothelial cells in However, vascular endothelial cells in the experimental group showed that cytochondria were swelling; endocytoplasmic reticulum was amplified; chromatin margination was clear; nucleus was in pyknosis; endothelial cells fell down from basal membrane; cell Severely, it was shown that nuclear pyknosis was obvious, and this was like early apoptosis. CONCLUSION: Apoptosis of endothelial cells may occur in spasmodic vessels.