Physiological effects of a habituation procedure for functional MRI in awake mice using a cryogenic radiofrequency probe
Physiological effects of a habituation procedure for functional MRI in awake mice using a cryogenic radiofrequency probe
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DOI：
10.1016/j.jneumeth.2016.09.013
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发表时间：
2016-12
影响因子：
3
通讯作者：
Keitaro Yoshida;Y. Mimura;Ryosuke Ishihara;Hiroshi Nishida;Yuji Komaki;Tomohito Minakuchi;T. Tsurugizawa;Masaru Mimura;H. Okano;Kenji F. Tanaka;N. Takata
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文献类型：
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作者：
Keitaro Yoshida;Y. Mimura;Ryosuke Ishihara;Hiroshi Nishida;Yuji Komaki;Tomohito Minakuchi;T. Tsurugizawa;Masaru Mimura;H. Okano;Kenji F. Tanaka;N. Takata
背景小鼠功能磁共振成像（fMRI）通常在麻醉下进行，因为使用牙棒和耳塞的传统三点固定方法很难稳定保持清醒小鼠的头部。尽管一些研究通过在头骨上安装头柱在清醒小鼠身上成功进行了功能磁共振成像，但这不能应用于使用高信噪比 (SNR) 低温 MRI 探测器 CryoProbe 的功能磁共振成像，因为它紧密覆盖了小鼠的头部。新方法我们开发了适用于使用 CryoProbe 进行 fMRI 的清醒小鼠的头部固定工具。结果通过手术将头杆固定在小鼠的头骨上，然后小鼠习惯于模拟功能磁共振成像环境，每天两小时，持续八天，对体重、粪便重量、肌电图 (EMG) 和心电图进行生理检查。肌电图功率仅在习惯一天后就会下降，而心率在至少习惯七天后就会下降。功能磁共振成像期间清醒小鼠的估计头部运动明显小于体素大小。出乎意料的是，清醒小鼠的功能磁共振成像信号的时间信噪比高于用传统方法保持的麻醉小鼠。麻醉和清醒小鼠大脑中的功能连接均显示出双侧和单侧网络。之前已使用 CryoProbe 对麻醉小鼠进行了与现有方法的 fMRI 比较。我们的方法在习惯或功能磁共振成像期间不使用麻醉剂。结论我们的方法将有利于在小鼠和人类中使用功能磁共振成像的转化研究，因为人类功能磁共振成像通常是在没有麻醉剂的情况下进行的。
BackgroundFunctional magnetic resonance imaging (fMRI) in mice is typically performed under anesthesia due to difficulties in holding the head of awake mice stably with a conventional three-point fixation method that uses a tooth-bar and earplugs. Although some studies have succeeded in fMRI in awake mice by attaching a head-post on the skull, this cannot be applied to fMRI using a high signal-to-noise ratio (SNR) cryogenic MRI-detector, CryoProbe, because it covers the head of a mouse closely.New methodWe developed head-fixation implements for awake mice that are applicable to fMRI using CryoProbe.ResultsA head-bar was surgically attached to the skull of a mouse that was then habituated to a mock fMRI-environment, two hours/day for eight days with physiological examinations of body-weight, fecal weight, electromyogram (EMG), and electrocardiogram. EMG power decreased with just one day of habituation, whereas heart rate decreased after at least seven days of habituation. Estimated head motions of awake mice during fMRI were significantly smaller than a voxel size. Unexpectedly, temporal SNR of fMRI signals for awake mice was higher than that for anesthetized mice held by a conventional method. Functional connectivity in the brain of both anesthetized and awake mice showed bilateral and unilateral networks.Comparison with existing method(s)fMRI using CryoProbe had been performed on anesthetized mice previously. Our method does not use anesthetics during habituation or fMRI.ConclusionOur method would be beneficial for translational research using fMRI in mice and humans because human fMRI is typically performed without anesthetics.