Voltage-Clamp Experiment

 

The patch clamp is a special voltage clamp that allows to resolve currents flowing through single ion channels.

 

The characteristics of a patch clamp are:

 

(1) The currents measured are very small, on the order of picoamperes in single-channel recording and usually up to several nanoamperes in whole-cell recording.

 

(2) Due to the small currents, particularly in single-channel recording, the electrode polarizations and nonlinearities are negligible.

 

(3) An Ag/AgCl electrode can record the voltage accurately even while passing current.

 

(4) Voltage clamp also simplifies the measurement of currents flowing through the whole-cell membrane, particularly in small cells that cannot be easily penetrated with electrodes.

 

(5) The electronic ammeter must be carefully designed to avoid adding appreciable noise to the currents it measures.