Recording from membrane ion channels (patch clamp)
Erwin Neher and Bert Sakmann developed a technique which allows the minute currents which flow through the ion channels of cell membranes to be amplified and recorded. The changes in current that result from the opening and closing of a single ion channel can be observed, and their properties studied.
Ion channels allow small, charged particles to travel into and out of cells, changing the electrochemical gradient across the cell membrane. In neurons this allows the creation of a difference in electrical potential across the cell membrane, so that the cell acts as a capacitor. When the neuron is stimulated the stored charge allows the cell to fire electrical impulses. Electrochemical properties of nerve impulses were described by Hodgkin and Huxley, and for many years electrophysiologists studied squid, because their large nerve cells, allowed changes in current across a cell membrane to be recorded.
Neher and Sakmann refined their equipment to record the tiny changes in current generated by a single ion channel, and devised a way of isolating single or small numbers of channels, while using Hodgkin and Huxley’s methods to control the voltage across the cell membrane.
Working with cells from frogs and rats, they used a thin pipette – a glass tube with a tip diameter so small that it was only visible under a microscope. When the tip of the pipette contacted the cell membrane, suction was applied to pull the membrane tightly around the tip. This formed a tight seal with a very high electrical resistance between the glass pipette and the cell membrane, so that a small section of the membrane – the part sucked up inside the pipette - was electrically isolated. When an ion channel in the cell membrane opened and the charged ions moved through the resulting current could be recorded.
Tags
Research Fields: Cell biology, Brain & nervous system, Drugs & toxins(yes - 3 items)Date: 1991 (required)
Scientist(s): Erwin Nehar, Bert Sakmann (required)
Countries: Germany(yes - 1 items)
Animals Used: Rat, Frog(required - 2 items)
Description: . (yes)
Medical Applications: Basic research(yes - 1 items)
