| Objective: The establishment of the brainstem ischemic model is meaningful to the research of pathology, pathophysiology and pharmacology of lesions of brain stem, but few models have been developed in China and abroad at present, different methods and different animals are used. Most domestic research focus on large animals such as dogs. Comparing with these animals, rats have many advantages, so we choose rats to establish the brain stem ischemic model, earlier changes of pathology were observed and effects on blood flow after brain stem ischemia were investigated.Method: Male wistar rats were divided into operative group and sham-operative group. The basilar artery were surgically exposed and coagulated at two points in operative group, in sham-operative group only the dura matter was incised but basilar artery was not occluded. Neural symptoms were observed after basilar artery occlusion. Coverage and degree of ischemia were defined with methylene and TTC stain. The value of blood flow was measured with the technique of laser-Dopplar before basilar artery occlusion and respectively at 30,60, 120 minutes after basilar artery occlusion. Animals were killed respectively at 2,6,12,24 hours after basilar artery occlusion, tissues of brainstem were got and observed with light microscope and electron microscope.Result: After two-point occlusions of basilar artery nervous symptoms appeared. They were irregular breathing, convulsion, singultus, dilation of pupils, bluntness of light reflex, nystagmus, extremities paralysis and stupor. The coverage of ischemia mainly located in pons and part of superior medulla stained with methylene and TTC. Local blood flows on brainstem decreased significantly after two-point occlusions of basilar artery. Light microscope: 2 hours after occlusion neuronal nuclear stain to deepen , cell body shrinkage and Nissl bodies decrease were observed; 6 hours after occlusion few neuonal karyopyknosis, cell body shrinkage and lysis were observed, degeneratede necrotic foci , myelin sheath disappearance, hemorrhage of blood vessel were also observed; 12 hours afterocclusion myelin sheath disappearance was more severe; 24 hours after occlusion neuronal degenerated necrosis was more prominant than before, myelin sheath disruption and disappearance were shown in some area. Electron microscope: 2 hours after occlusion neuroplasm and nucleus were slightly edemafous, chromatin of nucleolus was discrete, apoptotic tendency was also observed in nucleolus of astrocyte; 6 hours after occlusion cytoplasm distinct edema , complete degeneration and lysis of cytoplasm, many erythrocytes were observed outside blood vessel; 12 hours after occlusion neuronal mitochondrial edema was distinctive, there were more vacuoles, apoptotic nucleolus of astrocyte were observed and majority of synapses lost normal structure in;24 hours after occlusion only remained apoptotic nucleus of nerve cell and astrocyte were observed in 24 hours, organelle of cytoplasm were almost completely lost.Conclusion: 1)The symptoms of the loss of nervous function induced by two-point occlusions of basilar artery were irregular breathing, convulsion, hiccup, changes of pupils, nystagmus, paralysis, disturbance of consciousness. They are similar to the symptoms due to brainstem infarction in clinical patients. This model simulates some courses of clinical pathology. (2)2 hours after brainstem ischemia ultra-early changes of pathology were observed, lesions of ischemia was aggravated gradually along with the prolongation of time. 3)Compared with before occlusion, local blood flow of brainstem decreased significantly after basilar artery occlusion. It suggests that the result of basilar artery occlusion is reliable, changes of blood kinetics is also investigated 4) Advantages of the model: the cerebral vessels of rats is similar to mankind's, the operation is relatively simple, the position of ischemia is constant, animals are not easily to die, replication is good and cost is low. The model is suitable to study pathology and pathoph...
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