Excitable cells can be studied by the great variety of techniques that are available for the study of living cells in general. These include light and electron microscopy, X-ray diffraction measurements, experiments involving radioactive tracers, cell fractionation techniques, cell imaging techniques, biochemical methods, and so on. The techniques which are particular to the study of excitable cells are those involving the measurement of rapid electrical events. So in order to understand the subject, we need to have some idea of how these measurements are made. Here we look briefly at some of the more general methods used. Duncan (1990) gives more detail on a variety of electrical measurement techniques.

Recording electrodes

If we wish to record the potential difference between two points, it is necessary to position electrodes at those points and connect them to a suitable instrument for measuring voltage. It is desirable that these electrodes should not be affected by the passage of small currents through them, i.e. that they should be non-polarizable. For many purposes fine silver wires are quite adequate. Slightly better electrodes are made from platinum wire or from silver wire that has been coated electrolytically with silver chloride. For very accurate measurements of steady potentials, calomel half-cells (mercury/mercuric chloride electrodes) may have to be used.

If the site we wish to record from is very small in size (such as occurs in extracellular recording from cells in the central nervous system), the electrode must have a very fine tip, and be insulated except at the end.