Wu G, Ekedahl R, Hallin R G
Department of Medical Laboratory Sciences and Technology, Huddinge University Hospital, Karolinska Institute, Sweden.
Exp Brain Res. 1998 Jun;120(4):470-8. doi: 10.1007/s002210050420.
Percutaneous microneurography is a powerful technique allowing studies of activity in single nerve fibres of conscious humans. However, the mechanisms by which single-unit recordings are achieved with this technique are not fully understood. To further elucidate these mechanisms, dual-lead recordings, using a modified concentric needle electrode with two separate recording surfaces at the tip, were performed in normal subjects. Sixty-two single units supplied by large myelinated afferents were studied. The majority (90%) of the units were recorded simultaneously on both surfaces but with different action potential amplitudes. Four types of unitary waveforms were encountered. The potentials recorded on the two channels were of the same type, although occasionally some details differed. Parallel waveform changes of the same units occurred simultaneously on the two surfaces. A displacement of a single fibre from one recording surface to the other with or without concomitant waveform-type transitions was observed when the electrode was slightly repositioned intraneurally. The results provided direct evidence to confirm that concentric needle electrodes record single-unit activity extracellularly from myelinated nerve fibres, probably at or close to a node of Ranvier. All the types of action potentials encountered with conventional tungsten electrodes were also identified in dual-channel recordings with concentric electrodes, which casts doubt on the previous explanation that single-unit activity recorded with tungsten electrodes is derived from intracellular sources. Some biological and technical aspects of the findings are discussed, especially concerning the applicability of in vivo measurements of the time course of the action potentials in humans and ways to improve microneurography towards multichannel recordings.
经皮微神经ography是一种强大的技术，可用于研究清醒人类单根神经纤维的活动。然而，利用该技术实现单单位记录的机制尚未完全明了。为进一步阐明这些机制，在正常受试者中使用一种改良的同心针电极（其尖端有两个独立的记录表面）进行了双导联记录。研究了由大的有髓传入纤维支配的62个单单位。大多数（90%）单位在两个表面上同时被记录到，但动作电位幅度不同。遇到了四种类型的单位波形。在两个通道上记录到的电位属于同一类型，尽管偶尔有些细节有所不同。同一单位的平行波形变化在两个表面上同时发生。当电极在神经内稍微重新定位时，观察到单根纤维从一个记录表面移位到另一个记录表面，伴有或不伴有波形类型的转变。这些结果提供了直接证据，证实同心针电极从有髓神经纤维细胞外记录单单位活动，可能是在郎飞结处或其附近。在同心电极的双通道记录中也识别出了传统钨电极所遇到的所有类型的动作电位，这对先前关于用钨电极记录的单单位活动源自细胞内的解释提出了质疑。讨论了这些发现的一些生物学和技术方面，特别是关于人类动作电位时间过程的体内测量的适用性以及改进微神经ography以实现多通道记录的方法。
