Biological Membranes - A. N. Ogurtsov 2012

Electrogenesis of Biomembranes
Ion Channels
The Patch-Clamp Technique for Ion Channel Research

A true revolution in ion channel research was achieved in 1976 by Erwin Neher and Bert Sakmann (awarded the 1991 Nobel Prize in Physiology or Medicine "for their discoveries concerning the function of single Ion Channels in Cells"). They proposed using Glass microelectrode pipettes (with a slightly thicker tip than those traditionally used for measuring membrane potentials). Instead of penetrating the membrane, the micropipette tip is firmly pressed against The Cell surface and, by applying a slight suction, sealed onto the membrane patch (Figure 97).

This patch-clamp technique increased the sensitivity of electrical measurements more than 100-fold and made it possible to study the function of a single ion channel in real time, as observation was restricted solely to the patch of biomembrane enclosed within the micropipette tip. The tight seal between the micropipette and the biomembrane surface provides an exceptionally high electrical resistance (extremely low electrical conductance) in the gigaohm range (1 GΩ = 10⁹ Ω). Such a gigaseal ensures that the electrical current flowing through the micropipette is identical to the current passing through the patch of biomembrane attached to the tip.

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Figure 97 - Schematic diagram of patch-clamp recording: top - attachment of the glass micropipette (1) to the biomembrane surface (4) forming a tight seal (3), enclosing only two ion channels (2) within the tip of the micropipette. Bottom - four standard configurations of patch-clamp recording

The patch-clamp technique allows researchers to record The activity of a single ion channel—monitoring current fluctuations between the open and closed states with microsecond temporal resolution (Figure 98).

Furthermore, a major advantage of this method is The ability to study ion channel function in their native membrane environment, specifically within an intact cell.

Four standard configurations of patch-clamp recording. The patch-clamp technique is remarkably versatile. It allows both for measurements on intact cells (Figure 97(a)) and for manipulating excised membrane patches.

For example, one can "excise" the membrane patch containing ion channels attached to the micropipette tip (Figure 97(б)) or rupture the membrane patch to establish direct continuity between the Cytosol and the interior of the electrode (whole-cell mode), thereby monitoring the activity of all ion channels in the cell (Figure 97(в)).

Figure 98 - Patch-clamp signal of an Acetylcholine Receptor

Finally, by detaching the membrane patch from the cell, researchers can simulate Changes in the intracellular chemical environment by introducing specific substances through the relatively wide-bore recording micropipette (Figure 97(г)).