Wegener Susanne, Wong Eric C
Department of Radiology, University of California at San Diego, San Diego, CA 92103, USA.
NMR Biomed. 2008 Aug;21(7):696-703. doi: 10.1002/nbm.1243.
MRI is a powerful tool for measuring cerebral blood flow (CBF) longitudinally. However, most animal studies require anesthesia, potentially interfering with normal physiology. Isoflurane anesthesia was used here to study CBF regulation during repetitive scanning in rats. MR perfusion images were acquired using FAIR (flow-sensitive alternating inversion recovery) arterial spin labeling, and absolute CBF was calculated. CBF changes in response to a hypoxic (12% O2) and hypercapnic (5% CO2) gas stimulus were monitored. Hypercapnia led to a robust increase in CBF compared with baseline (195.5+/-21.5 vs 123.6+/-17.9 ml/100 g/min), and hypoxia caused a smaller non-significant increase in mean CBF values (145.4+/-13.4 ml/100 g/min). Strikingly, when measurements were repeated 5 days later, CBF was dramatically reduced in hypoxia (93.2+/-8.1 ml/100 g/min) compared with the first imaging session. Without application of the hypoxic and hypercapnic gases during the first MRI, baseline CBF and CBF changes in response to hypoxia at the second MRI were similar to naive rats. Blood gas analyses revealed a slight reduction in arterial oxygenation during the second period of anesthesia compared with the first. These findings indicate that, in isoflurane-anesthetized rats, even a short hypoxic episode can have long-lasting effects on cerebrovascular regulation.
磁共振成像（MRI）是纵向测量脑血流量（CBF）的强大工具。然而，大多数动物研究需要麻醉，这可能会干扰正常生理功能。本研究使用异氟烷麻醉来研究大鼠重复扫描期间的CBF调节。使用FAIR（血流敏感交替反转恢复）动脉自旋标记采集磁共振灌注图像，并计算绝对CBF。监测对低氧（12% O2）和高碳酸血症（5% CO2）气体刺激的CBF变化。与基线相比，高碳酸血症导致CBF显著增加（195.5±21.5 vs 123.6±17.9 ml/100 g/min），而低氧导致平均CBF值出现较小的、无统计学意义的增加（145.4±13.4 ml/100 g/min）。引人注目的是，5天后重复测量时，与第一次成像相比，低氧状态下的CBF显著降低（93.2±8.1 ml/100 g/min）。在第一次MRI期间不应用低氧和高碳酸血症气体时，第二次MRI时的基线CBF和对低氧的CBF变化与未处理大鼠相似。血气分析显示，与第一次相比，第二次麻醉期间动脉氧合略有降低。这些发现表明，在异氟烷麻醉的大鼠中，即使是短暂的低氧发作也可能对脑血管调节产生长期影响。
