Voltage clamping of Xenopus laevis oocytes utilizing agarose-cushion electrodes

Pflugers Arch. 1994 Mar;426(5):453-8. doi: 10.1007/BF00388310.


Two-electrode voltage clamping of expressed ion channels in intact oocytes of the South African clawed frog Xenopus laevis has been refined to allow stable, low-resistance electrical access to the cytosol (50-800 k omega). Glass microelectrodes were filled with a cushion of 1% agarose at their tips to prevent KCl leakage (agarose-cushion electrodes). Insertion of these electrodes into X. laevis oocytes yielded stable preparations for periods of more than 1 h with a stable input resistance of 1-4 M omega. Furthermore, a simple modification of the voltage-clamp circuit (charging compensator) is described that increases the flexibility of arrangements for differential recording of the membrane potential in order to subtract voltage drops across a series resistance. The result is a considerable increase in the practically attainable speed of the voltage clamp with the conventional two-electrode arrangement. The performance of the charging compensator was tested on an equivalent circuit that simulates the oocyte and electrodes. In addition, the combination of agarose-cushion electrodes and the charging compensator was tested on oocytes expressing Shaker H4 currents. The fidelity of the voltage-clamp circuit was also verified by measuring the membrane potential with additional independent microelectrodes connected to a differential amplifier, independent of the two-electrode voltage clamp system. The system described here will be useful for ion channel studies in X. laevis oocytes requiring long-term recordings and/or measurements of large, fast ion currents.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cytosol / physiology
  • Electric Stimulation
  • Female
  • Ion Channels / physiology
  • Microelectrodes*
  • Models, Biological
  • Oocytes / physiology*
  • Sepharose*
  • Xenopus laevis / physiology*


  • Ion Channels
  • Sepharose