The interpretation of current-voltage relations recorded from a spherical cell with a single microelectrode.

An analysis is presented of the displacement of potential recorded when one microelectrode is used both to apply current to and record potential from a spherical cell. There are three significant components of the displacement in potential: a component produced inside the microelectrode, a time-independent component representing the spatially nonuniform flow of current in the immediate vicinity of the microelectrode, and a time-dependent spatially uniform component representing the average potential across the cell membrane. The second component describes changes in the potential across the cell membrane as well as potential drops in the interior of the cell, the importance of each factor being dependent on the location of the electrode. Simple expressions, derived by a theoretical treatment, are given for each component of potential. The implications for the interpretation of experimental results determined with the "single-electrode bridge" technique are discussed and an optimal balancing procedure is suggested.