The
voltage clamp is an experimental method used by
electrophysiologists to measure the
ion currents through the
membranes of excitable cells, such as
neurons, while holding the membrane
voltage at a set level. A basic voltage clamp will iteratively measure the
membrane potential, and then change the membrane potential (voltage) to a desired value by adding the necessary current. This "clamps" the cell membrane at a desired constant voltage, allowing the voltage clamp to record what currents are delivered. Because the currents applied to the cell must be equal to (and opposite in
charge to) the current going across the cell membrane at the set voltage, the recorded currents indicate how the cell reacts to changes in membrane potential. Cell membranes of excitable cells contain many different kinds of
ion channels, some of which are
voltage-gated. The voltage clamp allows the membrane voltage to be manipulated independently of the ionic currents, allowing the
current-voltage relationships of membrane channels to be studied.