MAGNETIC COIL STIMULATION OF STRAIGHT AND BENT AMPHIBIAN AND MAMMALIAN PERIPHERAL-NERVE INVITRO - LOCUS OF EXCITATION
MAGNETIC COIL STIMULATION OF STRAIGHT AND BENT AMPHIBIAN AND MAMMALIAN PERIPHERAL-NERVE INVITRO - LOCUS OF EXCITATION
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DOI：
10.1113/jphysiol.1993.sp019467
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发表时间：
1993-01-01
影响因子：
5.5
通讯作者：
CRACCO, RQ
中科院分区：
文献类型：
--
作者：
MACCABEE, PJ;AMASSIAN, VE;CRACCO, RQ
1.根据经典的电缆理论，磁线圈（MC）应在感应电场的负向一阶空间导数处激励均匀介质中的线性神经纤维。这种预测进行了测试，MC刺激哺乳动物膈神经和两栖动物坐骨神经和分支在体外，浸泡在林格氏溶液中的槽内，并确定兴奋的网站，通过记录响应类似的潜伏期局部电刺激。随后，将识别的激发位点与感应电场的测量值及其计算的一阶空间导数进行比较。一个特殊的硬件设备被用来选择性地反转MC电流方向，并产生主要是单相或多相诱导的脉冲分布，其初始相位是相同的极性，形状和幅度。当使用两栖动物神经准备时，并发症是与切断分支相关的低阈值点兴奋。双相电流的抑制导致潜伏期的变化，其变化大致对应于诱导的阴极和阳极之间的距离。每个兴奋部位的位置位于或非常接近平行于直神经测量的感应电场的负向一阶空间导数峰值。值得注意的是，神经的兴奋没有发生在“8字”MC结中心上方的感应电场的峰值处。一个多相脉冲在两个部位都兴奋神经，在一个部位是负向的第一相，大约150 μ s后，在另一个部位是反向的负向的第二相。当感应电流流向记录电极时，多相和双相脉冲引起的反应具有相似的潜伏期。用不导电的固体有机玻璃圆柱体跨在神经上产生了局部空间狭窄和感应电场的增加，导致兴奋阈值降低。当MC电流方向反向时，一阶空间导数峰之间的间距相应地更近，表现为潜伏期偏移显著减少。当神经弯曲并且感应电流沿着神经朝向弯曲定向时，在那里兴奋阈值降低。将弯曲的角度从0度增加到90度以上，对阈值的降低进行分级。在直神经中，当电流朝向切断端时，阈值最低。在低阈值点（由一对圆柱体或弯曲在神经上以及在神经末梢处产生）处的最佳激励发生在感应电场的峰值附近或峰值内，而不是在其一阶导数处。当调整MC输出强度和移动的连接区域的MC在神经的长轴3厘米朝向或远离一个低阈值点，反应引起在几乎相同的潜伏期，这意味着一个共同的网站的兴奋。可能，这些观察结果与人类中缺乏延迟转移的例子有关。
1. According to classical cable theory, a magnetic coil (MC) should excite a linear nerve fibre in a homogeneous medium at the negative-going first spatial derivative of the induced electric field. This prediction was tested by MC stimulation of mammalian phrenic and amphibian sciatic nerve and branches in vitro, immersed in Ringer solution within a trough, and identifying the sites of excitation by recording responses of similar latency to local electrical stimulation. Subsequently, the identified sites of excitation were compared with measurements of the induced electric field and its calculated first spatial derivative. A special hardware device was used to selectively reverse MC current direction and to generate predominantly monophasic- or polyphasic-induced pulse profiles whose initial phases were identical in polarity, shape and amplitude. When using the amphibian nerve preparation, a complication was excitation at low threshold points related to cut branches.2. Reversal of monophasic current resulted in latency shifts corresponding approximately to the distance between induced cathode and anode. The location of each site of excitation was at, or very near, the negative-going first spatial derivative peaks of the induced electric field measured parallel to the straight nerve. Significantly, excitation of the nerve did not occur at the peak of the induced electric field above the centre of the 'figure of eight' MC junction.3. A polyphasic pulse excited the nerve at both sites, by the negative-going first phase at one location, and approximately 150 mus later, by the reversed negative-going second phase at the other location. Polyphasic and monophasic pulses elicited responses with similar latency when the induced current flowed towards the recording electrode.4. Straddling a nerve with non-conducting solid lucite cylinders created a localized spatial narrowing and increase in the induced electric field, resulting in a lowered threshold of excitation. The corresponding closer spacing between first spatial derivative peaks was exhibited by a significant reduction in latency shift when MC current direction was reversed.5. When a nerve is bent and the induced current is directed along the nerve towards the bend, the threshold of excitation is reduced there. Increasing the angle of the bend from 0 deg to more than 90 deg graded the decrease in threshold.6. In a straight nerve the threshold was lowest when current was directed towards the cut end.7. Optimal excitation at a low threshold point (created on the nerve by a pair of cylinders or a bend, and at a nerve ending) occurs near or within the peak of the induced electric field, rather than at its first derivative. When adjusting MC output intensity and moving the junction region of the MC in the long axis of the nerve 3 cm towards or away from a low threshold point, responses were elicited at nearly identical latency, implying a common site of excitation. Possibly, these observations relate to examples in the human where a latency shift is lacking.