A simple intrapipette salt bridge.

A simple method is described for achieving a salt bridge within a patch pipette. The tip of the pipette is filled with a Cl(-)-free solution that bathes the membrane patch. Above this is a Cl(-)-containing solution that surrounds the recording Ag/AgCl wire electrode. Addition of 0.07% (w/v) agarose to the solution in the tip prevents bulk mixing of the 2 phases within the pipette. This configuration makes it possible to remove Cl- from the membrane surface but maintain it at the electrode surface. The presence of the Cl(-)-free phase in the bottom of the patch pipette does not reduce the electrical stability of the recording electrode.