A novel voltage clamp technique for mapping ionic currents from cultured skeletal myotubes

Area of Science:

• Electrophysiology
• Cellular Neuroscience
• Biophysics

Background:

• Ion channel biophysical properties and distribution are crucial for electrically excitable cell function.
• Standard patch-clamp voltage clamp techniques are insufficient for mapping low-density ion channel distributions.

Purpose of the Study:

• To introduce and validate a novel voltage clamp method, the whole-cell loose patch (WCLP) method.
• To assess the WCLP method's suitability for mapping ion channel distributions, particularly in large cells with low channel densities.

Main Methods:

• Developed the WCLP method, integrating whole-cell recording (tight-seal pipette) with focal extracellular stimulation (loose-seal pipette).
• Applied the WCLP method to cultured chick myotubes to record evoked patch currents.
• Employed deconvolution techniques to correct for signal filtering caused by cell cable properties and pipette series resistance.

Main Results:

• The WCLP method successfully evoked and recorded membrane currents.
• Identified significant signal filtering effects dependent on stimulation-recording pipette distance.
• Demonstrated accurate recovery of patch membrane currents using deconvolution based on determined filter impulse responses.

Conclusions:

• The WCLP method is effective for mapping ion channel distributions, even at low densities.
• Signal filtering is a critical factor in WCLP recordings, but can be accurately corrected.
• This technique offers a valuable tool for studying ion channel localization in complex cellular preparations.