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Ion trapping with fast-response ion-selective microelectrodes enhances detection of extracellular ion channel gradients

By Mark A. Messerli, Leon P. Collis and Peter J.S. Smith


Previously, functional mapping of channels has been achieved by measuring the passage of net charge and of specific ions with electrophysiological and intracellular fluorescence imaging techniques. However, functional mapping of ion channels using extracellular ion-selective microelectrodes has distinct advantages over the former methods. We have developed this method through measurement of extracellular K+ gradients caused by efflux through Ca2+-activated K+ channels expressed in Chinese hamster ovary cells. We report that electrodes constructed with short columns of a mechanically stable K+-selective liquid membrane respond quickly and measure changes in local [K+] consistent with a diffusion model. When used in close proximity to the plasma membrane (<4 ?m), the ISMs pose a barrier to simple diffusion, creating an ion trap. The ion trap amplifies the local change in [K+] without dramatically changing the rise or fall time of the [K+] profile. Measurement of extracellular K+ gradients from activated rSlo channels shows that rapid events, 10–55 ms, can be characterized. This method provides a noninvasive means for functional mapping of channel location and density as well as for characterizing the properties of ion channels in the plasma membrane

Topics: QH301
Year: 2009
OAI identifier:
Provided by: e-Prints Soton

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  1. (1991). A deconvolution technique for improved estimation of rapid changes in ion concentration recorded with ion-selective microelectrodes. doi
  2. (1994). A practical guide to the preparation of Ca 2+ buffers. doi
  3. (1987). Analysis of whole cell currents to estimate the kinetics and amplitude of underlying unitary events: relaxation and 'noise' analysis.
  4. (1997). Carrier-based ion-selective electrodes and bulk optodes. 1. General characteristics. doi
  5. (2004). Chloride fluxes in lily pollen tubes: a critical reevaluation. doi
  6. (2006). Electrochemical sensor applications to the study of molecular physiology and analyte flux in plants. doi
  7. (2006). Fabrication and use of high-speed, concentric H +- and Ca 2+-selective microelectrodes suitable for In vitro extracellular recording. doi
  8. (2000). Functional localization of single active ion channels on the surface of a living cell. doi
  9. Funtional characteristics of two BKCa channel variants differentially expressed in rat brain tissues. doi
  10. (2001). Ion Channels of Excitable Membranes. Sinauer Associates, doi
  11. (1986). Ion-selective microelectrodes doi
  12. (1969). Liquid ion-exchanger microelectrodes. In doi
  13. (1980). Low-impedance, coaxial, ion-selective, double-barrel microelectrodes and their use in biological measurements. doi
  14. (2007). Measuring extracellular ion gradients from single channels with ion-selective microelectrodes. doi
  15. (1996). Miniature endplate current rise times <100 µs from improved dual recordings can be modeled with passive acetylcholine diffusion from a synaptic vesicle. doi
  16. (2001). Monte Carlo methods for simulating realistic synaptic microphysiology using MCell. In Computation Neuroscience: Realistic Modeling for Experimentalists. doi
  17. (1993). mSlo, a complex mouse gene encoding 'maxi&quot; calcium-activated potassium channels. doi
  18. (2005). Optical patch-clamping&quot;: Single-channel recording by imaging Ca 2+ flux through individual muscle acetylcholine receptor channels. doi
  19. (2005). Optical patch-clamping&quot;: Single-channel recording by imaging Ca2+ flux through individual muscle acetylcholine receptor channels. doi
  20. (2003). Optical single-channel recording: imaging Ca 2+ flux through individual N-type voltage-gated channels expressed in Xenopus oocytes. doi
  21. (2003). Optical single-channel recording: imaging Ca2+ flux through individual N-type voltage-gated channels expressed in Xenopus oocytes. doi
  22. (1992). Patch voltage clamping with low-resistance seals: loose patch clamp. doi
  23. (2007). Principles, development and applications of self-referencing electrochemical microelectrodes to the determination of fluxes at cell membranes. doi
  24. (1982). Properties of single calciumactivated potassium channels in cultured rat muscle. doi
  25. (1991). Proton modulation of a Ca 2+-activated K + channel from rat skeletal muscle incorporated into planar bilayers. doi
  26. (1999). Self-referencing, non-invasive, ion selective electrode for single cell detection of transplasma membrane calcium flux. doi
  27. (2005). The Handbook: A guide to fluorescent probes and labelling technologies.
  28. (1987). Valinomycin-based K+ selective microelectrodes with low electrical membrane resistance. doi

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