| Backgrounds and purpose:Aneurysmal subarachoid hemorrhage is a devastating condition,with mortality rates approaching 50% in the first month after rupture.Research of the pathogenesis of the aneurysm will help to prevent the intracranial aneurysm from occurrence,to control the development of it ,to minimize the rate of rapture,and to improve the prognosis of treatment.How to creating an ideal aneurysm model of animal is the difficulty and key of this studies. At present,there are many means to creat aneurysm models,such assurgical,interventional, hemodynamic,drug-induced,but this models have some distance from ideal model.Through dropping elastase solution on adventitiaes of artery to induce aneurysm,the pathology presentations are almost consistent with human's cerebral aneurysm,the method is simple and repeatiable easily,the cost is low.But there are some disputes about the perfect concentration, quantity of elastase solution, the influence of ligating one lateral common carotid artery, the morphologic changes of early period of aneurysm models formation and the long effect of aneurysm models.We study the perfect concentration, quantity of elastase solution, the influence of ligated a lateral common carotid artery, the morphologic changes of early period of anrurysm models formation and the long effect of aneurysm model in order to establish foundation of further study on the pathogenesis andtreatment of aneurysm.Methods.? 12 healthy New Zealand rabbits were randomly divided into 4 groups, measure the diameter of 4 point of vessel,which is the near heart points, namely 0.5cm,1.5cm,2.5cm,3.5cm, of bifurcation of commom carotid artery;dropping bilaterally elastase solution 1 V- l,the concentrations are 0.5u/u l,1.0u/u l,1.5u/u 1 and 3.0u/u 1, 0.5 V-1 every time,measuring the diameters of vessels from 5 minutes to 1 hour after dropping.? 12 healthy New Zealand rabbits were randomly divided into 4 groups, dropping bilaterally 1.5u/u 1 elastase solution 1.0 u 1 one time and 0.5 u 1, 1.0 u 1, 2.0 n 1, 0.5 u 1 every time, measuring the diameters of vessels and observing the figure changes from 5 minutes to 1 hour after dropping. (3)42 healthy New Zealand rabbits were randomly divided into 5 groups.-sham operation group A(n=6),sham operation group B(n=6),operation group C(n=12), operation group D(n=12), operation group E(n=6).A lateral common carotid artery of half rabbits of every group are ligated.The elastase solution 1 ul with concentration of 1.5u/ul was dropped on adventitiaes of rabbits' common carotid artery,0.5 U 1 every time;the sham operation groups are dropped with NS on the same point. The samples of aneurysm model are collected for HE and Weighter stainning, A,C group are collected after 1 day after operation,B,D groups are collected after 7 day after operation and observing the changes of vital signs,diameter of vessels and whether the vessels are open.E group are observed 2months continuous,two rabbit's neck are dissected in order to observe the vessel and whether the vessels are open. Results: ?The difference of vessels diameter has statistic significanceafter dropping different concentration elastase solutions on the point of adventitiaes of rabbits' common carotid artery,the diameter of 1.5u/ul group is the biggest; the diameter has no statistic significance between 30 minutes and lhour after dropping in this group.(2)The difference of vessels diameter has statistic significance after dropping different quantity of elastase solution,0.5 u 1 group is least, the other three groups have no difference,but the numbers of fusifrom aneurysm have different,2/6 in 1.0 n 1 group,every time 0.5 u 1 ;4/6 in 2.0 u 1 group,every time 0.5 U 1; 5/6 in one time 1.0 u 1 group.(3)We used 1.5u/ u 1 elastase solution 1.0 u l,every time 0.5 u l.,to drop on adventitiaes of rabbits' common carotid arterys.In this way,we created 45 aneurysms on 30 rabbits,including 36 lateral saccular aneurysm and 9 fusifrom aneurysm.The vital signs are no statistic significance between pre- and postoperation,no death occurred postoperation. ?Clipped one side of CCAs have no influence on the blood pressure and the width and height of aneurysms. ?Pathology changes:The elastin of artery wall is demolished,but doesn't disappear, smooth muscle cells is intact on 1st day postoperation. On the 7th day postoperation,the local elastin almost disappear, smooth muscle cells degeneration distinctly.In contrast groups,though also have inflammatory cells infiltration,there is no elastin and smooth muscle cells degeneration. ?In the observation after postoperation,no spontaneous rupture,two rabbit's neck are dissected,we find the vessels are open ,the heighth of aneurysm are 3.82 and 4.01mm,the width are 2.79 and 2.98mm,no significance difference between this and 7th postoperation,but local vessels whited and inflammatory hyperplasia is obvious.?The diameter of 4 pointof commom carotid artery have no significance difference. Conclusion: ?1.5u/u 1 elastase solution 1.0ul,every time 0.5 u 1 is preferably concentration and quantity in this way.(2)In our study ,through dropping on the same place of adventitiaes of rabbits' common carotid artery to creat aneurysm models is simple, repeatable and representative pathological characters.The models can be used in the study of aneurysm' pathogeny,the reasons of dialation and rapture,intervention therapy.(3)The demolish of elastin of artery wall is important initially,the infiltration of inflammation cell prick up degeneration of extracellular matrix and smooth muscle cells of vessels.The inhibitors of elastase and inflammatory cells infiltration could be used to treat aneurysms.@Ligation one side common carotid artery isn't necessary in creating aneurysm model.?There are some different between model and the human'only through elastase ,we didn't observed the spontous rapture of models and enlargement,the local inflammation is obvious. ?The dropping point is the plane of cricoid cartilage,the place is superficial and convenient to operation.
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