Vollmer D G, Takayasu M, Dacey R G
Department of Neurosurgery, Washington University School of Medicine, St. Louis, Missouri.
J Neurosurg. 1992 Jul;77(1):113-9. doi: 10.3171/jns.1992.77.1.0113.
The reactivity of rabbit basilar artery and penetrating arteriolar microvessels was studied in vitro using an isometric-tension measurement technique and an isolated perfused arteriole preparation, respectively. Comparisons were made between reactivities of normal vessels and those obtained from animals subjected to experimental subarachnoid hemorrhage (SAH) 3 days prior to examination. Subarachnoid hemorrhage produced significant increases in basilar artery contraction in response to increasing concentrations of serotonin (5-hydroxytryptamine) (10(-9) to 10(-5) M) and prostaglandin F2 alpha (10(-9) to 10(-5) M) when compared to normal arteries. In addition, SAH attenuated the relaxing effect of acetylcholine following serotonin-induced contraction and of adenosine triphosphate after KCl-induced basilar artery contractions. In contrast to the changes observed in large arteries, cerebral microvessels did not demonstrate significant differences in spontaneous tone or in reactivity to a number of vasoactive stimuli including application of calcium, serotonin, and acetylcholine. On the other hand, small but significant changes in arteriolar responsiveness to changes in extraluminal pH and to application of KCl were noted. Findings from this study suggest that intracerebral resistance vessels of the cerebral microcirculation are not greatly affected by the presence of subarachnoid clot, in contrast to the large arteries in the basal subarachnoid space. The small changes that do occur are qualitatively different from those observed for large arteries. These findings are consistent with the observation of significant therapeutic benefit with the use of calcium channel blockers without changes in angiographically visible vasospasm in large vessels. It is likely, therefore, that calcium antagonists may act to decrease total cerebrovascular resistance at the level of the relatively unaffected microcirculation after SAH without changing large vessel diameter.
分别采用等长张力测量技术和离体灌注小动脉制备方法，在体外研究了兔基底动脉和穿通小动脉微血管的反应性。对正常血管与检查前3天经历实验性蛛网膜下腔出血（SAH）的动物所获血管的反应性进行了比较。与正常动脉相比，蛛网膜下腔出血使基底动脉对血清素（5-羟色胺）（10⁻⁹至10⁻⁵M）和前列腺素F2α（10⁻⁹至10⁻⁵M）浓度增加的收缩反应显著增强。此外，SAH减弱了血清素诱导收缩后乙酰胆碱的舒张作用以及氯化钾诱导基底动脉收缩后三磷酸腺苷的舒张作用。与在大动脉中观察到的变化相反，脑微血管在自发张力或对包括钙、血清素和乙酰胆碱在内的多种血管活性刺激的反应性方面未显示出显著差异。另一方面，注意到小动脉对管腔外pH变化和氯化钾应用的反应性有微小但显著的变化。本研究结果表明，与基底蛛网膜下腔的大动脉相比，脑微循环的脑内阻力血管不受蛛网膜下腔血凝块的显著影响。确实发生的微小变化在性质上与在大动脉中观察到的变化不同。这些发现与使用钙通道阻滞剂可获得显著治疗益处且大血管造影可见的血管痉挛无变化的观察结果一致。因此，钙拮抗剂可能在SAH后相对未受影响的微循环水平上起到降低总脑血管阻力的作用，而不改变大血管直径。
