Measuring Reversal Potentials
The reversal potential refers to the membrane potential at which the current changes its flowing direction. For electrophysiological measurements, the change in direction can either mean inward currents becoming outward currents at a specific voltage or vice versa. Using reversal potential measurements allows the experimenter to determine ion specificity of a receptor/channel as well as the driving force of ions through the receptor/channel at a given voltage. For example, if the reversal potential measured for a given channel is close the reversal potential for K+, it is likely that the receptor/channel is predominantly permeable to K+. This chapter discusses the approaches that can be used to measure the reversal potentials of the isolated currents. In addition, we discuss technical considerations that can enhance the accuracy of the measurements.