Burdett N G, Menon D K, Carpenter T A, Jones J G, Hall L D
Herchel Smith Laboratory for Medicinal Chemistry, Cambridge, UK.
Magn Reson Imaging. 1995;13(4):549-53. doi: 10.1016/0730-725x(95)00010-e.
Autoradiographic studies have shown that low dose ketamine produces increases in regional glucose utilisation and blood flow in the hippocampus, cerebral cortex, and olfactory lobe in the rat brain, probably due to antagonism at the NMDA receptor. Functional MRI using deoxyhaemoglobin contrast can be used to study changes in regional cerebral blood flow (rCBF). Long TE gradient-echo sequences were used to study changes in rCBF produced by low dose ketamine in rats anaesthetised with nitrous oxide, supplemented with either halothane (HAL) or fentanyl/fluanisone/midazolam (FFM) combination. Images from rats in the FFM group showed a 10-14% increase in signal intensity in the hippocampus, cerebral cortex, and olfactory lobe following either a single bolus or a low dose infusion of ketamine (p < .05). These changes were significantly reduced in the HAL group (p < .005). Halothane is known to attenuate the changes in regional glucose utilisation produced by the noncompetitive NMDA antagonist dizocilpine (MK-801), and its effects on ketamine-induced changes in rCBF seen in this study may be due to a similar effect. The potential use of functional MRI in studying the effect of pharmacological interventions on rCBF is discussed.
放射自显影研究表明，低剂量氯胺酮可使大鼠脑海马体、大脑皮层和嗅叶的局部葡萄糖利用率和血流量增加，这可能是由于其对N-甲基-D-天冬氨酸（NMDA）受体的拮抗作用。利用脱氧血红蛋白造影的功能磁共振成像（fMRI）可用于研究局部脑血流量（rCBF）的变化。采用长回波时间（TE）梯度回波序列，研究低剂量氯胺酮对用一氧化二氮麻醉、并用氟烷（HAL）或芬太尼/氟胺酮/咪达唑仑（FFM）组合辅助麻醉的大鼠rCBF的影响。FFM组大鼠的图像显示，单次推注或低剂量输注氯胺酮后，海马体、大脑皮层和嗅叶的信号强度增加了10 - 14%（p <.05）。在HAL组中，这些变化显著降低（p <.005）。已知氟烷可减弱非竞争性NMDA拮抗剂地佐环平（MK - 801）引起的局部葡萄糖利用率变化，本研究中其对氯胺酮诱导的rCBF变化的影响可能是由于类似的作用。文中讨论了功能磁共振成像在研究药物干预对rCBF影响方面的潜在用途。
