背景:近来提出的临界关闭压在脑血流自动调节中起着关键作用,是脑循环的有效下游压,可客观反映动态调节的脑血管紧张度,即血管平滑肌收缩舒张的功能状态。目的:利用临界关闭压动态评价高血压对脑微动脉平滑肌收缩功能的损伤及其与病理形态改变间的关系。设计:随机对照的实验。单位:广州医学院第二附属医院神经科学研究所、中山大学附属第一医院神经科。材料:实验于2002-07/2003-08在中山大学生理科学实验室进行。选择健康雄性SD大鼠160只,随机分为对照组和高血压组,每组80只。方法:高血压组用双肾双夹法复制成易卒中型肾血管性高血压大鼠模型。对照组除不上银夹外,其余处理同高血压组。两组动物在术后的第2,4,6,8,10,12,14及16周8个时间点各随机选取10只进行动脉血压、临界关闭压的测定。测定完毕后在麻醉状态下取大鼠额顶叶脑组织,制成切片,定量分析脑微动脉的形态变化。主要观察指标:①两组大鼠术后不同时间点动脉血压、临界关闭压。②两组大鼠术后不同时间点脑微动脉形态参数。结果:160只大鼠均进入结果分析。①高血压组平均动脉压于术后第6周起明显升高,均显著高于对照组(P<0.05)。②高血压组大鼠术后脑血管临界关闭压逐步升高,于术后14,16周明显高于对照组[(63.75±7.43),(37.28±3.68)mmHg;(67.37±15.57),(38.39±7.41)mmHg,P<0.05]。③高血压组大鼠脑内微动脉的中膜厚度增加非常明显,于第8周后显著大于对照组(P<0.05)。④临界关闭压的升高与平均动脉压、脑内微动脉的中膜厚度呈正相关(r=0.90693,0.81136,P均<0.05)。并且血压升高的初期和血压较高后临界关闭压变化较明显,于血压上升明显期则改变不显著,呈倒“S”形改变(R2=0.9962,P<0.05)。结论:高血压形成后脑微动脉平滑肌的收缩程度随动脉血压的动态升高而加强,血管紧张度相应提高,并且在高血压初期和血压较高后改变比较明显。 BACKGROUND: The recently proposed critical closure pressure plays a key role in the automatic regulation of cerebral blood flow and is an effective downstream pressure of the cerebral circulation. It can objectively reflect the dynamic regulation of cerebrovascular tone, which is the functional state of contraction and relaxation of vascular smooth muscle. OBJECTIVE: To assess the effect of hypertension on the contractile function of smooth muscle of cerebral arterioles and its relationship with the pathological changes by using the critical closure pressure. Design: Randomized controlled experiment. Unit: Institute of Neuroscience, Second Affiliated Hospital of Guangzhou Medical College, Department of Neurology, First Affiliated Hospital of Sun Yat-sen University. Materials: The experiment was performed at the Physiology Science Laboratory of Sun Yat-sen University from July 2002 to August 2003. 160 healthy male SD rats were randomly divided into control group and hypertension group, 80 in each group. Methods: Hypertension group was double-kidney double-cloned into rat model of stroke-induced renovascular hypertension. In addition to the control group not on the silver clip, the rest deal with the high blood pressure group. Two groups of animals were randomly selected at 8, 6, 6, 8, 10, 12, 14, and 16 weeks after operation for arterial blood pressure and critical closure pressure. After the measurement, the frontal lobe brain tissue of rats was taken under anesthesia, and the slices were made into slices to quantitatively analyze the morphological changes of cerebral arterioles. MAIN OUTCOME MEASURES: ① Arterial blood pressure and critical pressure at different time points after operation in both groups. ② The morphological parameters of cerebral arterioles at different time points after operation in both groups. Results: 160 rats were involved in the result analysis. ① The mean arterial pressure in hypertensive group increased significantly from the 6th week after operation, which were significantly higher than those in the control group (P <0.05). (2) The critical Closure of cerebrovascular in hypertensive rats increased gradually after operation, and were significantly higher at 14 and 16 weeks after operation (63.75 ± 7.43, 37.28 ± 3.68 mmHg, 67.37 ± 15.57, 38.39 ± 7.41) mmHg, P <0.05]. (3) The intima-media thickness of cerebral arteries in hypertensive rats increased significantly, which was significantly greater than that of the control group after 8 weeks (P <0.05). The increase of critical closure pressure was positively correlated with mean arterial pressure and medial thickness of cerebral arterioles (r = 0.90693,0.81136, P <0.05). The changes of critical closure pressure were more obvious in the early period of high blood pressure and high blood pressure, but not obvious in the period of obvious rise of blood pressure, with an inverted “S” shape (R2 = 0.9962, P <0.05). CONCLUSION: The contraction of smooth muscle of cerebral arterioles after hypertension is enhanced with the dynamic increase of arterial blood pressure, the corresponding increase of vascular tone, and more obvious in the early stage of hypertension and after the high blood pressure.