Voltage Clamps

The voltage clamp is used by electrophysiologists to measure the ion currents across a neuronal membrane while holding the membrane voltage at a set level. Neuronal membranes 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.

The concept of the voltage clamp is due to Kenneth Cole and George Marmount in the 1940s. Cole discovered that it was possible to use two electrodes and a feedback circuit to keep the cell's membrane potential at a level set by the experimenter.

Alan Hodgkin realized that to understand ion flux across the membrane, it was necessary to eliminate differences in membrane potential. After experiments with the voltage clamp, Hodgkin and Andrew Huxley outlined the ionic causes of the action potential in 1952, for which they shared the 1963 Nobel Prize in Physiology or Medicine.