Stenroos Petteri, Paasonen Jaakko, Salo Raimo A, Jokivarsi Kimmo, Shatillo Artem, Tanila Heikki, Gröhn Olli
Kuopio Biomedical Imaging Unit, A.I.V. Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
Charles River Discovery Research Services Finland Oy, Kuopio, Finland.
Front Neurosci. 2018 Aug 20;12:548. doi: 10.3389/fnins.2018.00548. eCollection 2018.
Functional magnetic resonance imaging (fMRI) is a powerful noninvasive tool for studying spontaneous resting state functional connectivity (RSFC) in laboratory animals. Brain function can be significantly affected by generally used anesthetics, however, rendering the need for awake imaging. Only a few different awake animal habituation protocols have been presented, and there is a critical need for practical and improved low-stress techniques. Here we demonstrate a novel restraint approach for awake rat RSFC studies. Our custom-made 3D printed restraint kit is compatible with a standard Bruker Biospin MRI rat bed, rat brain receiver coil, and volume transmitter coil. We also implemented a progressive habituation protocol aiming to minimize the stress experienced by the rats, and compared RSFC between awake, lightly sedated, and isoflurane-anesthetized rats. Our results demonstrated that the 3D printed restraint kit was suitable for RSFC studies of awake rats. During the short 4-day habituation period, the plasma corticosterone concentration, movement, and heart rate, which were measured as stress indicators, decreased significantly, indicating adaptation to the restraint protocol. Additionally, 10 days after the awake MRI session, rats exhibited no signs of depression or anxiety based on open-field and sucrose preference behavioral tests. The RSFC data revealed significant changes in the thalamo-cortical and cortico-cortical networks between the awake, lightly sedated, and anesthetized groups, emphasizing the need for awake imaging. The present work demonstrates the feasibility of our custom-made 3D printed restraint kit. Using this kit, we found that isoflurane markedly affected brain connectivity compared with that in awake rats, and that the effect was less pronounced, but still significant, when light isoflurane sedation was used instead.
功能磁共振成像（fMRI）是一种强大的非侵入性工具，用于研究实验动物的静息态功能连接（RSFC）。然而，常用的麻醉剂会显著影响脑功能，因此需要进行清醒状态下的成像。目前仅提出了几种不同的清醒动物适应方案，迫切需要实用且改进的低应激技术。在此，我们展示了一种用于清醒大鼠RSFC研究的新型束缚方法。我们定制的3D打印束缚套件与标准的布鲁克生物自旋MRI大鼠床、大鼠脑接收线圈和容积发射线圈兼容。我们还实施了一种渐进式适应方案，旨在尽量减少大鼠所经历的应激，并比较了清醒、轻度镇静和异氟烷麻醉大鼠之间的RSFC。我们的结果表明，3D打印束缚套件适用于清醒大鼠的RSFC研究。在为期4天的短暂适应期内，作为应激指标测量的血浆皮质酮浓度、活动和心率显著下降，表明大鼠适应了束缚方案。此外，在清醒MRI扫描后10天，基于旷场和蔗糖偏好行为测试，大鼠没有表现出抑郁或焦虑的迹象。RSFC数据显示，清醒、轻度镇静和麻醉组之间的丘脑-皮质和皮质-皮质网络存在显著变化，强调了清醒成像的必要性。本研究证明了我们定制的3D打印束缚套件的可行性。使用该套件，我们发现与清醒大鼠相比，异氟烷显著影响脑连接性，而使用轻度异氟烷镇静时，这种影响虽不那么明显，但仍然显著。
