Intraspinal microstimulation excites multisegmental sensory afferents at lower stimulus levels than local α-motoneuron responses
Intraspinal microstimulation excites multisegmental sensory afferents at lower stimulus levels than local α-motoneuron responses
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DOI：
10.1152/jn.00061.2006
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发表时间：
2006-12-01
影响因子：
2.5
通讯作者：
Ellaway, P. H.
中科院分区：
文献类型：
--
作者：
Gaunt, R. A.;Prochazka, A.;Ellaway, P. H.
脊髓运动区的微刺激通常被认为可以激活电极尖端附近的运动神经元和本体脊髓神经元。然而，先前的研究表明，灰质中的椎管内微刺激（ISMS）激活了感觉传入轴突和α -运动神经元（MNs）。在这里，我们报告了随着ISMS振幅的增加，感觉传入轴突和MNs的招募。在4只急性失觉猫（其中2只为慢性脊髓化）脊髓L-5-L-7节背角、中间区和腹角植入微丝，对其进行脊髓内微刺激。通过背根的神经电图记录检测到感觉轴突的激活。后肢肌肉肌电图（EMG）记录检测MNs的激活。感觉轴突几乎总是在较低的刺激水平下被激活，而与刺激电极的位置无关。肌电图反应潜伏期随着ISMS刺激强度的增加而降低，表明MNs首先经突触激活，然后随着刺激强度的增加而直接激活。ISMS在刺激部位的背根细丝中诱导了反激活性，其进入区可达吻侧和尾侧17毫米。我们假设传入神经的局部末端分支所激发的动作电位反方向传播到传入神经的所有末端分支，并通过突触刺激远离刺激部位的MNs和中间神经元。这可能有助于解释为什么局灶性ISMS可以激活肌肉的许多MNs，即使它们分布在细长的列中。
Microstimulation within the motor regions of the spinal cord is often assumed to activate motoneurons and propriospinal neurons close to the electrode tip. However, previous work has shown that intraspinal microstimulation (ISMS) in the gray matter activates sensory afferent axons as well as alpha-motoneurons (MNs). Here we report on the recruitment of sensory afferent axons and MNs as ISMS amplitudes increased. Intraspinal microstimulation was applied through microwires implanted in the dorsal horn, intermediate region and ventral horn of the L-5-L-7 segments of the spinal cord in four acutely decerebrated cats, two of which had been chronically spinalized. Activation of sensory axons was detected with electroneurographic recordings from dorsal roots. Activation of MNs was detected with electromyographic (EMG) recordings from hindlimb muscles. Sensory axons were nearly always activated at lower stimulus levels than MNs irrespective of the stimulating electrode location. EMG response latencies decreased as ISMS stimulus intensities increased, suggesting that MNs were first activated transsynaptically and then directly as intensity increased. ISMS elicited antidromic activity in dorsal root filaments with entry zones up to 17 mm rostral and caudal to the stimulation sites. We posit that action potentials elicited in localized terminal branches of afferents spread antidromically to all terminal branches of the afferents and transsynaptically excite MNs and interneurons far removed from the stimulation site. This may help explain how focal ISMS can activate many MNs of a muscle even though they are distributed in long thin columns.