Effects of hypoxia, hyperoxia, and hypercapnia on baseline and stimulus-evoked BOLD, CBF, and CMRO2 in spontaneously breathing animals
Effects of hypoxia, hyperoxia, and hypercapnia on baseline and stimulus-evoked BOLD, CBF, and CMRO2 in spontaneously breathing animals
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DOI：
10.1016/j.neuroimage.2004.12.010
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发表时间：
2005-04-15
期刊：
影响因子：
5.7
通讯作者：
Duong, TQ
中科院分区：
文献类型：
--
作者：
Sicard, KM;Duong, TQ
应用功能磁共振成像（fMRI）研究异氟醚麻醉下自主呼吸大鼠吸入低氧、高氧和高碳酸气体对基线和刺激诱发的血氧水平依赖（BOLD）信号、脑血流量（CBF）和脑氧代谢率（cmoro2）变化的影响。每只动物接受六种激励气体条件的基线期（9% O-2, 12% O-2, 21% O-2, 100% O-2, 5% CO2和10% CO2），然后是前爪刺激的叠加期。在初级体感觉皮层中发现了显著的刺激诱发的fMRI反应。前爪刺激的相对fMRI反应在不同的气体条件下不同，依赖于基线生理，而绝对fMRI反应在中等气体条件下相似（12% 02,21% 02,100% 02和5% CO2），相对独立于基线生理。与使用成熟技术获得的数据一致，基线和刺激诱发的cm2在中度生理扰动中是不变的，因此支持cm2 - fmri技术用于非侵入性cm2 - m2测量。然而，在9%的O-2和10%的CO2下，刺激诱发的CBF和BOLD大幅减少，cmor2的形式似乎无效，这可能是由于神经血管耦合减弱和/或模型在极端生理扰动下的失败。这些发现表明，绝对fMRI测量有助于区分神经和非神经对fMRI信号的贡献，并可能在改变的基础生理状态下更准确地测量大脑活动。此外，由于许多药物、病理生理状态和精神状况改变了独立于神经活动的基线生理，这些结果对使用相对功能磁共振成像变化来绘制大脑活动的神经影像学研究具有重要意义。(c) 2004 Elsevier Inc.版权所有。
Functional magnetic resonance imaging (fMRI) was used to investigate the effects of inspired hypoxic, hyperoxic, and hypercapnic gases on baseline and stimulus-evoked changes in blood oxygenation level-dependent (BOLD) signals, cerebral blood flow (CBF), and the cerebral metabolic rate of oxygen (CMRO2) in spontaneously breathing rats under isoflurane anesthesia. Each animal was subjected to a baseline period of six inspired gas conditions (9% O-2, 12% O-2, 21% O-2, 100% O-2, 5% CO2, and 10% CO2) followed by a superimposed period of forepaw stimulation. Significant stimulus-evoked fMRI responses were found in the primary somatosensory cortices. Relative fMRI responses to forepaw stimulation varied across gas conditions and were dependent on baseline physiology, whereas absolute fMRI responses were similar across moderate gas conditions (12% 02, 21% 02 100% 02, and 5% CO2) and were relatively independent of baseline physiology. Consistent with data obtained using well-established techniques, baseline and stimulus-evoked CMRO2 were invariant across moderate physiological perturbations thereby supporting a CMRO2-fMRI technique for non-invasive CMRO2 measurement. However, under 9% O-2 and 10% CO2, Stimulus-evoked CBF and BOLD were substantially reduced and the CMRO2 formalism appeared invalid, likely due to attenuated neurovascular coupling and/or a failure of the model under extreme physiological perturbations. These findings demonstrate that absolute fMRI measurements help distinguish neural from non-neural contributions to the fMRI signals and may lend a more accurate measure of brain activity during states of altered basal physiology. Moreover, since numerous pharmacologic agents, pathophysiological states, and psychiatric conditions alter baseline physiology independent of neural activity, these results have implications for neuroimaging studies using relative fMRI changes to map brain activity. (c) 2004 Elsevier Inc. All rights reserved.