Koide Masayo, Bonev Adrian D, Nelson Mark T, Wellman George C
Department of Pharmacology, University of Vermont College of Medicine, Burlington, VT 05405-0068, USA.
Acta Neurochir Suppl. 2013;115:167-71. doi: 10.1007/978-3-7091-1192-5_32.
The matching of blood flow to regional brain function, called functional hyperemia or neurovascular coupling, involves the coordinated activity of neurons, astrocytes, and parenchymal arterioles. Under physiological conditions, localized neuronal activation leads to elevated astrocyte endfoot Ca(2+) and vasodilation, resulting in an increase in cerebral blood flow. In this study, we examined the impact of subarachnoid hemorrhage (SAH) on neurovascular coupling. SAH model rats received two injections of autologous blood into the cisterna magna 24 h apart. Cortical brain slices from SAH model animals were prepared 4 days after the initial blood injection. Arteriolar diameter and astrocyte endfoot Ca(2+) were simultaneously measured using two-photon microscopy. As expected, neuronal activity evoked by electrical field stimulation (EFS) caused an elevation in endfoot Ca(2+) and vasodilation in brain slices from control animals. However, in brain slices from SAH animals, EFS induced a similar increase in astrocyte endfoot Ca(2+) that caused arteriolar constriction rather than vasodilation. Vasoconstriction was observed in approximately 90% of brain slices from SAH animals in response to EFS, with 40% exhibiting a sustained vasoconstriction, 30% exhibiting a transient vasoconstriction -(diameter restored within 1 min after EFS), and 20% responded with a biphasic response (brief vasodilation followed by -vasoconstriction). This inversion of neurovascular coupling may play a role in the development of neurological deficits following SAH.
血流与局部脑功能的匹配，即所谓的功能性充血或神经血管耦合，涉及神经元、星形胶质细胞和实质小动脉的协同活动。在生理条件下，局部神经元激活会导致星形胶质细胞终足Ca(2+)升高和血管舒张，从而使脑血流量增加。在本研究中，我们研究了蛛网膜下腔出血（SAH）对神经血管耦合的影响。SAH模型大鼠在相隔24小时的时间里分两次向小脑延髓池注射自体血。在首次注射血液4天后制备SAH模型动物的大脑皮质脑片。使用双光子显微镜同时测量小动脉直径和星形胶质细胞终足Ca(2+)。正如预期的那样，电场刺激（EFS）诱发的神经元活动导致对照动物脑片中终足Ca(2+)升高和血管舒张。然而，在SAH动物的脑片中，EFS诱导星形胶质细胞终足Ca(2+)出现类似的增加，但却导致小动脉收缩而非血管舒张。在SAH动物的约90%脑片中观察到对EFS的血管收缩反应，其中40%表现为持续性血管收缩，30%表现为短暂性血管收缩（EFS后1分钟内直径恢复），20%表现为双相反应（短暂血管舒张后接着血管收缩）。这种神经血管耦合的反转可能在SAH后神经功能缺损的发生中起作用。
