BACKGROUND & AIMS:
:This article describes the effects of dexmedetomidine (DEX) - the active ingredient of medetomidine, which is the latest popular sedative for functional magnetic resonance imaging (fMRI) in rodents - on multiple unit activity, local field potential (LFP), cerebral blood flow (CBF), pial vessel diameter [indicative of cerebral blood volume (CBV)], and blood oxygenation level-dependent (BOLD) fMRI. These measurements were obtained from the rat somatosensory cortex during 10 s of forepaw stimulation. We found that the continuous intravascular systemic infusion of DEX (50 μg/kg/h, doses typically used in fMRI studies) caused epileptic activities, and that supplemental isoflurane (ISO) administration of ~0.3% helped to suppress the development of epileptic activities and maintained robust neuronal and hemodynamic responses for up to 3 h. Supplemental administration of N(2)O in addition to DEX nearly abolished hemodynamic responses even if neuronal activity remained. Under DEX + ISO anesthesia, spike firing rate and the delta power of LFP increased, whereas beta and gamma power decreased, as compared with ISO-only anesthesia. DEX administration caused pial arteries and veins to constrict nearly equally, resulting in decreases in baseline CBF and CBV. Evoked LFP and CBF responses to forepaw stimulation were largest at a frequency of 8-10 Hz, and a non-linear relationship was observed. Similarly, BOLD fMRI responses measured at 9.4 T were largest at a frequency of 10 Hz. Both pial arteries and veins dilated rapidly (artery, 32.2%; vein, 5.8%), and venous diameter returned to baseline slower than arterial diameter. These results will be useful for designing, conducting and interpreting fMRI experiments under DEX sedation.
背景与目标:
: 本文介绍了右美托咪定 (DEX) -美托咪定的有效成分,美托咪定是啮齿动物功能磁共振成像 (fMRI) 的最新流行镇静剂-对多单位活动,局部场电位 (LFP),脑血流 (CBF),血管直径 [指示脑血容量 (CBV)] 和血氧水平依赖性 (BOLD) fMRI。这些测量值是在前爪刺激10 s期间从大鼠体感皮层获得的。我们发现,连续血管内全身输注DEX (50 μ g/kg/h,通常用于fMRI研究的剂量) 引起癫痫活动,并且〜0.3% 的补充异氟烷 (ISO) 给药有助于抑制癫痫活动的发展,并在长达3小时的时间内保持强大的神经元和血液动力学反应。除DEX外,补充施用N(2)O几乎消除了血液动力学反应,即使神经元活性仍然存在。在DEX ISO麻醉下,与仅ISO麻醉相比,尖峰放电速率和LFP的 δ 功率增加,而 β 和 γ 功率降低。DEX给药导致腰肌动脉和静脉几乎相等地收缩,导致基线CBF和CBV降低。诱发的LFP和CBF对前爪刺激的反应在8-10Hz的频率下最大,并且观察到非线性关系。类似地,在9.4 T处测量的BOLD fMRI响应在10 hz的频率下最大。腰肌动脉和静脉均迅速扩张 (动脉,32.2%; 静脉,5.8%),并且静脉直径恢复到基线的速度比动脉直径慢。这些结果将有助于在DEX镇静下设计,进行和解释fMRI实验。