A MEA-based Assay of Adrenal Chromaffin Cells Spontaneous Firing Using Ion Channel Blockers

Chromaffin cells express high-densities of Na+, Ca2+ and K+ channels and are able to fire action potentials when depolarized by pA currents. Their electrical activity determines the level of intracellular Ca2+ that controls the vesicular release of adrenaline and noradrenaline. Cultured rat chromaffin cells (RCCs) fire spontaneously at lowfrequencies (0.5-1.5 Hz) in a tonic or burst mode. Two open issues concerning RCCs spontaneous activity are still unanswered: is the firing a true physiological phenomenon or a consequence of cell alteration during intracellular recordings? How many RCC firing-modes do exist and what is their physiological function? We answered these questions using a MEA-based assay and ion channel modulators to understand the ability of these cells to fire spontaneously and to extend our knowledge regarding the involvement of different ion channel conductances in the modulation of the MEA-recorded action potentials shape