Imaging Department, Merck Research Laboratories, West Point, PA 19486, USA.
Neuroimage. 2012 Jan 16;59(2):1168-79. doi: 10.1016/j.neuroimage.2011.08.002. Epub 2011 Aug 11.
This study aims to identify fMRI signatures of nociceptive processing in whole brain of anesthetized rats during noxious electrical stimulation (NES) and noxious mechanical stimulation (NMS) of paw. Activation patterns for NES were mapped with blood oxygen level dependent (BOLD) and cerebral blood volume (CBV) fMRI, respectively, to investigate the spatially-dependent hemodynamic responses during nociception processing. A systematic evaluation of fMRI responses to varying frequencies of electrical stimulus was carried out to optimize the NES protocol. Both BOLD and CBV fMRI showed widespread activations, but with different spatial characteristics. While BOLD and CBV showed well-localized activations in ipsilateral dorsal column nucleus, contralateral primary somatosensory cortex (S1), and bilateral caudate putamen (CPu), CBV fMRI showed additional bilateral activations in the regions of pons, midbrain and thalamus compared to BOLD fMRI. CBV fMRI that offers higher sensitivity compared to BOLD was then used to compare the nociception processing during NES and NMS in the same animal. The activations in most regions were similar. In the medulla, however, NES induced a robust activation in the ipsilateral dorsal column nucleus while NMS showed no activation. This study demonstrates that (1) the hemodynamic response to nociception is spatial-dependent; (2) the widespread activations during nociception in CBV fMRI are similar to what have been observed in (14)C-2-deoxyglucose (2DG) autoradiography and PET; (3) the bilateral activations in the brain originate from the divergence of neural responses at supraspinal level; and (4) the similarity of activation patterns suggests that nociceptive processing in rats is similar during NES and NMS.
本研究旨在识别麻醉大鼠在足部接受有害电刺激（NES）和有害机械刺激（NMS）时全脑的疼痛处理的 fMRI 特征。分别使用血氧水平依赖（BOLD）和脑血容量（CBV）fMRI 来映射 NES 的激活模式，以研究疼痛处理过程中的空间依赖性血液动力学反应。对不同电刺激频率的 fMRI 反应进行了系统评估，以优化 NES 方案。BOLD 和 CBV fMRI 均显示出广泛的激活，但具有不同的空间特征。虽然 BOLD 和 CBV 在同侧背柱核、对侧初级体感皮层（S1）和双侧尾状核（CPu）中显示出很好的局部激活，但与 BOLD fMRI 相比，CBV fMRI 还显示出双侧脑桥、中脑和丘脑区域的额外激活。与 BOLD 相比，提供更高灵敏度的 CBV fMRI 用于比较同一动物中 NES 和 NMS 期间的疼痛处理。大多数区域的激活相似。然而，在延髓中，NES 诱导同侧背柱核的强烈激活，而 NMS 则没有激活。这项研究表明：（1）疼痛反应的血液动力学反应是空间依赖性的；（2）CBV fMRI 中疼痛时的广泛激活与 14C-2-脱氧葡萄糖（2DG）放射自显影和 PET 观察到的相似；（3）大脑中的双侧激活源自于脊髓水平以上的神经反应的发散；（4）激活模式的相似性表明大鼠在 NES 和 NMS 期间的疼痛处理相似。
