Neural sites involved in the sustained increase in muscle sympathetic nerve activity induced by inspiratory capacity apnea: a fMRI study
Neural sites involved in the sustained increase in muscle sympathetic nerve activity induced by inspiratory capacity apnea: a fMRI study
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DOI：
10.1152/japplphysiol.00588.2005
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发表时间：
2006-01-01
影响因子：
3.3
通讯作者：
Henderson, LA
中科院分区：
文献类型：
--
作者：
Macefield, VG;Gandevia, SC;Henderson, LA
最大吸气屏气（吸气能力呼吸暂停）对一个关闭的声门唤起大量和持续增加的肌肉交感神经活动（MSNA）。由于它依赖于高胸内压，有人认为这种操作导致低压压力感受器卸载，已知会增加MSNA。为了确定这种交感神经兴奋的中心起源，我们使用功能性磁共振成像来确定不同脑区激活的位点和时间过程。我们假设，正如先前Valsalvsa手法所显示的那样，大脑中离散但广泛的区域会参与其中。在15名健康受试者中，使用3-T扫描仪在连续3次吸气量为40 s的呼吸暂停期间收集了一系列90组梯度回波回波平面图像。计算全局信号强度变化，然后使用去趋势技术去除每个体素信号强度变化中的全局信号分量。在操作过程中，信号强度变化与已知MSNA模式之间的全脑相关性在逐体素的基础上进行，并通过随机效应分析程序确定显著变化（P < 0.01，未校正）。多个区域出现明显的信号增强，包括髓质吻侧外侧、小脑核、岛前部、下丘脑背内侧、前扣带和外侧前额叶皮层。信号强度降低发生在髓质背内侧和尾侧外侧、小脑皮层、海马和后扣带皮层。考虑到这些部位中的许多都在心血管控制中起作用，在吸气能力呼吸暂停期间，MSNA的持续增加可能源于一组分散的离散区域。
A maximal inspiratory breath hold (inspiratory capacity apnea) against a closed glottis evokes a large and sustained increase in muscle sympathetic nerve activity (MSNA). Because of its dependence on a high intrathoracic pressure, it has been suggested that this maneuver causes unloading of the low-pressure baroreceptors, known to increase MSNA. To determine the central origins of this sympathoexcitation, we used functional magnetic resonance imaging to define the loci and time course of activation of different brain areas. We hypothesized that, as previously shown for the Valsalvsa maneuver, discrete but widespread regions of the brain would be involved. In 15 healthy human subjects, a series of 90 gradient echo echo-planar image sets was collected during three consecutive 40-s inspiratory capacity apneas using a 3-T scanner. Global signal intensity changes were calculated and subsequently removed by using a detrending technique, which eliminates the global signal component from each voxel's signal intensity change. Whole brain correlations between changes in signal intensity and the known pattern of MSNA during the maneuver were performed on a voxel-by-voxel basis, and significant changes were determined by using a random-effects analysis procedure (P < 0.01, uncorrected). Significant signal increases emerged in multiple areas, including the rostral lateral medulla, cerebellar nuclei, anterior insula, dorsomedial hypothalamus, anterior cingulate, and lateral prefrontal cortexes. Decreases in signal intensity occurred in the dorsomedial and caudal lateral medulla, cerebellar cortex, hippocampus, and posterior cingulate cortex. Given that many of these sites have roles in cardiovascular control, the sustained increase in MSNA during an inspiratory capacity apnea is likely to originate from a distributed set of discrete areas.