| Research background: Spontaneous subarachnoid hemorrhage(SAH) is a commonlyhemorrhagic cerebrovascular emergency, and its most deadly complication is cerebralvasospasm(CVS), which is the major cause of high mortality and morbidity for the patients.Though the true mechanism of CVS had been intensive researched on for years, it remainunclear. Recently studies show that "calcitun over loading" and the increase of free radicals incells, may cause the promotion of cell apoptosis following activation of apoptotic genesequentially. The vascular contractile factors were increased and the vascular relaxant factorswere decreased following SAH, which can lead to vasospasm and proliferation of vascularsmooth muscle cells pathologically. Consequently, while apoptosis of endothelial cells happens,the proliferation of vascular smooth muscle cells exists in cerebral artery at the same time. Theunbalanced development of apoptosis and proliferation may play an important role in themechanism of CVS. As the natural antagon of calcium, magnesium has been more and morestudies focused on. Because of magnesium can prevent "calcium over loading", which is thecritical physiopathologic change of CVS after SAH, and relax vessels efficiently. But themechanism of anti-CVS effect of magnesium is still unclear. Its impact on the abnormalapoptosis and proliferation in cerebral arterial cells, what is the important cause CVS, has notbeen reported up to now.Objective: After rabbit SAH model was established, magnesium sulfate was injectedintravenous on experimental animals to prevent CVS, from the beginning to the end of thisexperiment. We evaluate the influence on apoptosis and proliferation of magnesium sulfate, toilluminate its mechanism of anti-CVS effect, through the observation of nervous function of theanimals and morphological changes, expression of Bcl-2,Bax and PCNA, as well as apoptoticindex of basilar artery.Materials and Methods: 30 rabbits were randomly divided into SAH group,treatmentgroup and control group. CVS model was established by using "double subarachnoid hemorrhage" which injecting arterial blood twice through the cisterna magna 48 hours apart, 2milliliter each time.①SAH group (n=10): Following the method as above.②control group(n=10): 2ml physiological saline solution was injected into cisterna magna instead of blood 48hours apart.③treatment group (n=10): Just 1 hour after the first injection of blood into cisternamagna, 250 milligram magnesium sulfate was used. In the coming days, 0.05gram magnesiumsulfate per a kilogram animals weight was injected intravenous each day, separated into twotimes. Meanwhile, equal dose of physiological saline solution was injected intravenous in SAHgroup and control group. After 7 days from the first blood injection, corresponding animalswere killed using perfusion-fixation and its basilar arteries were removed for the detection asfollowing techniques:①HE stain;②Transmission electron microscope;③Immunocytochemistry detection of Bcl-2,Bax and PCNA;④Tunel:Terminaldeoxynucleotidyl transferase-mediated deoxyuridine transphate-biotin nick endlabeling.Result: SAH group: The general state of health was poor and nervous function wasinsufficient in various degrees during the experiment. HE stain of basilar artery display thetypical morphological structural changes of CVS and the mean cross section proportion ofbasilar artery is much smaller than treatment group (P＜0.01). The ultrastructure was disorderedand cells were shown apoptotic changes in SAH group detected by transmission electronmicroscope. Apoptotic index is 71.26±9.32％in SAH group tested by Tunel, and compared withtreatment group and control group it was shown significant increase (P＜0.05). The expressionof Bax and PCNA were increased significantly, while Bcl-2 was decreased significantlycompared with treatment group detected by Immunocytochemistry (P＜0.05). All the results ofSAH group show that apoptosis and abnormal proliferation of arterial cells exist at the sametime after SAH, when the severe CVS happens. Treatment group: The general state of healthwas well and nervous function was no visible disfunction during the experiment, except fordecreasing diet amount occasionally. Morphological structural of basilar artery were obviouslyimprove in treatment group compared to SAH group. The mean cross section proportion ofbasilar artery is much larger than SAH group (P＜0.01), and no significant difference comparedto control group (P＞0.05). The ultrastructure pathological changes were slight in treatment group. Apoptotic index is 40.32±7.87%, which was significant decrease compared with SAHgroup (P＜0.01), though compared with control group (29.38±9.40%) it is also shownsignificant difference (P＜0.05). Immunocytochemistry results display that the expression ofBax and PCNA were decreased significantly, while Bcl-2 was increased significantly comparedwith SAH group (P＜0.05). The expression of Bcl-2, Bax and PCNA were no significantdifference between treatment group and control group (P＞0.05). All the results of treatmentgroup show that with the inhibition of apoptosis and abnormal proliferation of arterial cells, thebasilar artery was relaxed effectively and no visible CVS happens,, after magnesium sulfatewas injected.Conclusion:①Arterial cells apoptosis and abnormal proliferation exist at the same time afterSAH, and unbalanced development of these two factors may cause CVS happens.②With theeffect of vessels-dilation and neuroprotection, magnesium sulfate prevent and cure CVSeffectively, through inhibiting the apoptosis and abnormal proliferation of cerebral arterial cells,what were due to interdict the proliferative effect of vascular contractile factors andpathophysiological change after SAH.
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