Characterizing Extracellular Space in a Brain Slice Using Ion-Selective and Iontophoresis Microelectrodes

Begin with a recording chamber containing a secured thick brain slice immersed in artificial cerebrospinal fluid or aCSF.

This brain slice includes interstitial fluid and extracellular matrix, forming the interconnected extracellular space that surrounds brain cells.

Submerge the dual-channel ion-selective microelectrode and the iontophoresis microelectrode into the aCSF.

The dual-channel ion-selective microelectrode features a sensing channel for tetramethylammonium or TMA ions and a reference channel, while the iontophoresis microelectrode contains a TMA solution.

The iontophoresis electrode releases TMA ions, which diffuse toward the ion-selective microelectrode.

The sensing channel detects these TMA ions and generates an electrical signal. Record this as a baseline.

Insert both electrodes into the brain slice, keeping them slightly apart.

As the TMA ions diffuse through the extracellular space, they reach the ion-selective microelectrode.

Rerecord the signal and compare it with the baseline to analyze extracellular space properties, such as the volume fraction and the degree of twisting.