Ion-selective microelectrodes suitable for recording rapid changes in extracellular ion concentration

A method for fabricating double-barrel, ion-selective microelectrodes with fine tips (0.5-1.5 μm) and rapid response times is described. When made into K⁺-selective microelectrodes, the electrodes respond to changes in [K⁺]_o with a time constant of 70-95 ms. The electrical response of these electrodes to common-mode voltages can be made to have a time constant of < 2 ms, which minimizes electrical artifacts from field potentials. The application of these microelectrodes to the measurement of rapid, transient changes in retinal [K⁺]_o is presented.