Single-channel recording is achieved by pressing a fire-polished glass pipette, which has been filled with a suitable electrolyte solution, against the surface of a cell and applying light suction. Under such conditions, the glass pipette and the cell membrane will be less than 1 nm apart. The tighter the seal will have two advantages, 1) better electrical isolation of the membrane patch and 2) a high seal resistance reduces the current noise of the recording, permitting good time resolution of single channel currents, currents whose amplitude is in the order of 1 pA. Classically, three different configurations of the patched membrane can be used for single-channel recording: cell-attached, outside-out and inside-out patches. Cell-attached configuration contacts the cell membrane forming a gigaohm seal. Long-term stable recordings with low background noise can be performed in this configuration with minimal disruption to the intracellular milieu. For the outside-out configuration, the external surface of the patch is exposed to the external recording media. Offering the opportunity to repetitively expose the channels to different drugs and at various concentrations. In the inside-out patch configuration, it is the internal face of the membrane that is exposed to the external solution. This provides access to intracellular receptor binding sites and also enables studies of intracellular signaling pathways.
It is now possible to record single-channel current activity from many cell types, that is, from mammalian species, insects, invertebrates and also plants. The recording of single-channel currents enables detailed kinetic analyses of native and recombinant ion channels, including those that have been subject to natural or intended mutations to their structure.