Hsu E W, Hedlund L W, MacFall J R
Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina 27710, USA.
Magn Reson Med. 1998 Sep;40(3):421-6. doi: 10.1002/mrm.1910400312.
Functional mapping of the rat somatosensory cortex was performed with T2*-sensitized MRI using a forepaw electrical stimulation model in alpha-chloralose-anesthetized rats at 7 T under both normocapnia and mild hyperventilation-induced hypocapnia. A highly localized activation area, consistent with the known somatosensory cortical region, was detected in all seven animals studied during hypocapnia and in five of the same animals during normocapnia. Quantitatively, hypocapnia was found to significantly increase both the size of the fMRI activation area (3.4 +/- 0.6 mm2 versus 1.5 +/- 0.6 mm2 in normocapnia, mean +/- standard error, n = 7, P < 0.03) and the average fMRI signal intensity increase (3.4 +/- 0.6% versus 2.7 +/- 0.4%, n = 5, P < 0.05). The increased sensitivity of fMRI to functional activation may reflect a widened arterial-venous oxygenation difference resulting from an increased effective oxygen extraction during hyperventilation. The dependence of the fMRI response on the ventilation state underscores the need to control for physiological parameters in animal fMRI studies.
在7T磁场下，对用α-氯醛糖麻醉的大鼠，采用前爪电刺激模型，在正常碳酸血症和轻度过度通气诱发的低碳酸血症条件下，利用T2*敏感磁共振成像（MRI）对大鼠体感皮层进行功能映射。在低碳酸血症期间研究的所有7只动物以及在正常碳酸血症期间的同5只动物中，均检测到一个高度局部化的激活区域，该区域与已知的体感皮层区域一致。定量分析发现，低碳酸血症显著增加了功能磁共振成像（fMRI）激活区域的大小（正常碳酸血症时为1.5±0.6平方毫米，低碳酸血症时为3.4±0.6平方毫米，平均值±标准误差，n = 7，P < 0.03）以及fMRI信号强度的平均增加量（正常碳酸血症时为2.7±0.4%，低碳酸血症时为3.4±0.6%，n = 5，P < 0.05）。fMRI对功能激活的敏感性增加可能反映了过度通气期间有效氧提取增加导致的动静脉氧合差异扩大。fMRI反应对通气状态的依赖性强调了在动物fMRI研究中控制生理参数的必要性。
