Long term observation of propagating action potentials along the axon in a microtunnel device

The axon has a crucial role in the signal processing in the central nervous system. However, little is known about relationship between the structure of axons and conduction property of the axon. In this study, we developed a culture device to evaluate conduction velocity of relatively proximal (near the soma) and distal (far from the soma) parts of axons. The device has electrode units aligned at the bottom of the microtunnel structure. The electrode units enable the recording of action potentials of a single axon from three electrodes. Mouse cortical neurons were cultured in the device. The activity was recorded every five days. By employing an effective spike sorting method and a histogram method, propagating action potentials along the individual axon were successively detected from the spike trains which included the bursting activity. Finally, the change of the conduction delay at the distal part of axons was evaluated. The results show that our experimental system is feasible to study the conduction property of the axon.