Editing Electrophysiology (section)

===Sharp electrode recording===
In situations where one wants to record the potential inside the cell membrane with minimal effect on the ionic constitution of the intracellular fluid a sharp electrode can be used. These micropipettes (electrodes) are again like those for patch clamp pulled from glass capillaries, but the pore is much smaller so that there is very little ion exchange between the intracellular fluid and the electrolyte in the pipette. The electrical resistance of the micropipette electrode is reduced by filling with 2-4M KCl, rather than a salt concentration which mimics the intracellular ionic concentrations as used in patch clamping.<ref>Halliwell J., Whitaker M., Ogden D. (1994) Using microelectrodes. Microelectrode techniques: the Plymouth Workshop handbook. ed. Ogden, D. Available online at http://plymsea.ac.uk/id/eprint/7954/</ref> Often the tip of the electrode is filled with various kinds of dyes like [[Lucifer yellow]] to fill the cells recorded from, for later confirmation of their morphology under a microscope. The dyes are injected by applying a positive or negative, DC or pulsed voltage to the electrodes depending on the polarity of the dye.