A planar patch-clamp cartridge includes a common ground electrode through a conductive medium reaching into each extracellular chamber. The cartridge is first primed with intracellular solution injected from dispensing tips inserted from above into the intracellular chambers. Then the cartridge is rotated 180 degrees, whereby the intracellular and extracellular chambers assume face-down and face-up positions, respectively. Extracellular solution is then delivered using the same dispensing unit. A plurality of silver tubes engages the intracellular chambers at the end of the rotation to provide electrical conductivity and suction to the intracellular chambers.