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.

译文

:本文描述了右美托咪定(DEX)-美托咪定的活性成分-它是啮齿动物功能磁共振成像(fMRI)的最新流行镇静剂-对多种单位活性,局部场电位(LFP)和脑血流的影响(CBF),脉管直径[指示脑血容量(CBV)]和血液氧合水平依赖性(BOLD)fMRI。这些测量是在前脚刺激10 s的过程中从大鼠的体感皮层获得的。我们发现,持续进行的DEX(50μg/ kg / h,fMRI研究中通常使用的剂量)的血管内全身输注引起癫痫活动,补充异氟烷(ISO)的用量约0.3%有助于抑制癫痫活动的发展。维持强劲的神经元和血液动力学反应长达3小时。即使保留神经元活性,除DEX外,N(2)O的补充给药几乎消除了血流动力学反应。与仅使用ISO的麻醉相比,在DEX ISO麻醉下,峰值放电频率和LFP的德尔塔功率增加,而β和γ功率下降。施用DEX可使颈动脉和静脉几乎均等地收缩,从而导致基线CBF和CBV降低。诱发的LFP和CBF对前爪刺激的响应最大,频率为8-10 Hz,并且观察到非线性关系。同样,在9.4 T下测得的BOLD fMRI反应最大,频率为10 Hz。颈动脉和静脉都迅速扩张(动脉,占32.2%;静脉,占5.8%),静脉直径恢复到基线的速度比动脉直径慢。这些结果对于在DEX镇静下设计,进行和解释fMRI实验将是有用的。

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