The extracellular patch clamp: A method for resolving currents through individual open channels in biological membranes Excitable Tissues and Central Nervous Physiology Received: 23 December 1977 DOI:
Cite this article as: Neher, E., Sakmann, B. & Steinbach, J.H. Pflugers Arch. (1978) 375: 219. doi:10.1007/BF00584247 Abstract
The current contributions of individual ionic channels can be measured by electrically isolating a small patch of membrane. To do this, the tip of a small pipette is brought into close contact with an enzymatically cleaned membrane of a hypersensitive amphibian or mammalian muscle fiber. Current flowing through the pipette is measured. If the pipette contains cholinergic agonist at μ-molar concentrations, square pulse current waveforms can be observed which represent the activation of individual acetylcholine-receptor channels. The square pulses have amplitudes of 1 to 3 pA and durations of 10–100 ms.
In order to obtain the necessary resolution, a delicate compromise had to be found between different experimental parameters. Pipettes with 1–3 μm internal diameter and a steep final taper had to be used, extensive enzyme treatment was necessary, and conditions had to be found in which channels open at a relatively low frequency.
Key words Receptor Cholinergic Ionic channels Voltage clamp Membrane current Muscles References
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