Imaging and electrophysiology of individual neurites functionally isolated in microchannels

Abstract

The present chapter describes fabrication and utilization of neurite-isolation microelectrode arrays (NI-MEAs). The neurite-isolation device makes it possible to functionally isolate individual neurites from neuronal cell bodies as the neurites are forced to grow into narrow microchannels. Being microfluidic setups, the NI devices can be conveniently employed to carry out laser axotomy, study retrograde/anterograde transport in single axons, investigate the mutual effects of soluble factors (e.g., amyloid-β peptides) secreted by different neuronal populations (each “housed” in a different macrochannel), or to create the so-called axonal diodes imposing unidirectional axonal connectivity, to name but a few options. A separately made MEA is assembled with the NI device so that each of its microchannels is connected to one microelectrode. Unlike in patch-clamp, electrophysiology performed with the aid of NI-MEA is “massively parallel” as many neurites can be recorded simultaneously, and the data acquisition is noninvasive as the electrodes are not forced into a physical contact with the neurites. The capability of such setup is demonstrated here by recording the effects of different concentrations of nerve growth factor (NGF) on the electrical activity of individual neurites of superior cervical ganglions in primary culture, during their outgrowth into the microchannels. Simultaneous microscopic (e.g., immunofluorescence) observation of multiple neurites and their somata is an inherent extra option permitting to correlate their electrical activity with other physiological parameters, recorded by optical means.