Fig. (1) Schematic representations of four patch clamp configurations. (A) Cell-attached patch or on-cell patch. The electrode is tightly sealed to the patch of the membrane and the cell remains intact. (B) Whole cell patch. The tip of a micropipette is placed on a cell and suction is applied though the pipette to rupture the plasma membrane that directly accesses intracellular space. (C) Inside-out patch. After the gigaohm seal is formed, the micropipette is quickly withdrawn from the cell, leaving a patch of membrane attached to the micropipette and exposing the intracellular surface of the membrane to the medium. (D) Outside-out patch. After the whole-cell patch is formed, the electrode slowly withdraws from the cell, which allows the original outside of the membrane that faces outwards from the center of the electrode to form the patch.