Recording Saltatory Conduction Along Sensory Axons Using a High-Density Microelectrode Array

Abstract

Myelinated fibers are specialized neurological structures used for conducting action potentials quickly and reliably, thus assisting neural functions. Although demyelination leads to serious functional impairments, little is known the relationship between myelin structural change and increase in conduction velocity during myelination and demyelination processes. There are no appropriate methods for the long-term evaluation of spatial characteristics of saltatory conduction along myelinated axons. Herein, we aimed to detect saltatory conduction from the peripheral nervous system neurons using a high-density microelectrode array. Rat sensory neurons and intrinsic Schwann cells were cultured. Immunofluorescence and ultrastructure examination showed that the myelinating Schwann cells appeared at 1 month, and compact myelin was formed by 10 weeks in vitro. Activity of rat sensory neurons was evoked with optogenetic stimulation, and axon conduction was detected with high-density microelectrode arrays. Some conductions included high-speed segments with low signal amplitude. The same segment could be detected with electrical recording and immunofluorescent imaging for a myelin-related protein. The spatiotemporal analysis showed that some segments show a velocity of more than 2 m/s and that ends of the segments show a higher electrical sink, suggesting that saltatory conduction occurred in myelinated axons. Moreover, mathematical modeling supported that the recorded signal was in the appropriate range for axon and electrode sizes. Overall, our method could be a feasible tool for evaluating spatial characteristics of axon conduction including saltatory conduction, which is applicable for studying demyelination and remyelination.

The potential of in vitro neuronal networks cultured on micro electrode arrays for biomedical research

“…to identify one or more sources of APs, and to characterize their propagation in the neuronal network) [22]. With HD-MEAs, neuronal signals propagation can be characterized even at sub-cellular level, by tracking APs along neurons axons [136,137] (figure 2(d)).…”

“…These techniques can be used, for instance, to investigate how mutations, genetic variants, or the level of expression of certain proteins affect the electrophysiological phenotype observed at the network level [148,158,[160][161][162], but also to label or target specific neuronal populations (e.g. for optogenetic stimulation which allows to activate or inhibit specific neuronal populations [88,131,137,163]).…”

Large-area electrical imaging having single neuron resolution using 236,880 electrodes CMOS-MEA technology

“…CMOS-MEAs provide high temporal resolution, and therefore help trigger spontaneous signal propagation along the axonal arbors, such as in cultured primary hippocampus neurons and hiPSC-derived cortical neurons 15, 38, 109, 110 . Shimba’s group has also recorded signal conduction along myelinated DRG fibers under optical stimulation using a CMOS-MEA 111 . We recorded spontaneous axonal conduction dynamics in cultured DRG neurons in the present study using HD-CMOS-MEA.…”

Developing evaluation method for peripheral sensitization in cultured sensory neurons

“…In recent years, HD-MEA (High-Density MicroElectrode Array) [11][12][13] has been used to measure activity of neural cells. Though suffering from a low S/N ratio, HD-MEA features non-invasive measurement of cell electric potential to measure time evolution of activity.…”