Many ion channels, particularly potassium channels, are regulated by intracellular substances, such as nucleotides or Ca2+ . These modulators are washed out of the cell during standard whole-cell patch clamp recordings, or maintained at a particular concentration if they are included in the pipette solution. Perforated patch clamp recording permits electrical access between the cell and the patch pipette using pore-forming antibiotics such as nystatin or amphotericin B. These are permeable to small monovalent ions but present a physical barrier to the larger impermeable ions and molecules. This maintains the integrity of many cytoplasmic components including soluble second messengers, and also helps to prevent channel “run down”.
