Pressure-Polished Borosilicate Pipettes are “Universal Sealer” Yielding Low Access Resistance and Efficient Intracellular PerfusionPatch-Clamp Methods and Protocols

Whole-cell recording is the most widely used configuration of the patch recording technique, mainly because it allows to manipulate the intracellular environment while recording membrane current. However, the patch pipette tapered shank and the small tip opening give high access resistances and preclude efficient exchange between pipette solution and cell cytosol. Independently by the recording configuration, another problem of this technique is to gain consistently tight seals. Here it is described a method to enlarge the pipette shank without affecting the tip opening diameter, through the calibrated combination of heat and air pressure, with a custom made inexpensive set-up. These pressure polished pipettes give small access resistances, and allow the accommodation of pulled quartz or plastic perfusion tubes very close to the pipette tip (to deliver exogenous molecules into the cytosol with a controlled timing). Finally, it is also described a method to consistently attain seals with pipettes made from just one glass type, on a wide variety of cell types, isolated from different amphibian, reptilian, fish, and mammalian tissues, and on artificial membranes composed by many different lipid mixtures.