Liquid junction potentials and small cell effects in patch-clamp analysis.

TLDR: The aim of this review is to outline the contribution of such junction potentials and the errors resulting from measurements on small cells and to indicate how adequate junction potential corrections can be applied and the true values of underlying membrane parameters determined for such cells.

Abstract: Since the early 1980s, the patch-clamp technique (Hamill et al., 1981) has been of particular value in investigating the properties of ion channels in cells. When used in either the intact or excised configurations, the properties of individual ionic channels can be directly measured. In addition, the whole-cell configuration can be used to investigate the total response of the full complement of channels in a cell. The whole-cell configuration is of particular value in exploring the properties of very small cells which are not readily accessible to conventional microelectrode techniques. in all of the above measurements, there are two potential sources of error, in every situation there may be significant errors due to uncompensated junction potentials, which m a y a p p e a r to be eliminated by the normal zeroing procedure whereby residual potentials between pipette and bath solutions are offset prior to patch formation. In addition, in the intact and whole-cell patch configurations, the effect of the cells being small can introduce radical errors in the measurement of single-channel and whole-cell properties. The aim of this review is firstly to outline the contribution of such junction potentials and the errors resulting from measurements on small cells and secondly to indicate how adequate junction potential corrections can be applied and the true values of underlying membrane parameters determined for such cells. Where necessary, appropriate equations have been presented. Much of the material is a review of published work. However, the review also seeks to extend the implications of that work and, in particular, it also includes (in an appendix) a timedependent solution of the current relaxation following a channel closure.