Nanosecond electric pulse-induced increase in intracellular calcium in adrenal chromaffin cells triggers calcium-dependent catecholamine release

Experimental results on the effect of a single 5-6 ns, 5-7 MV/m electric pulse on electrically excitable bovine chromaffin cells are presented. Effects on intracellular calcium level were assessed by loading the cells with the calcium-sensitive fluorescence indicator calcium green and imaging the cells during nanosecond field exposure in microelectrode chambers that were fabricated on a glass microscope slide with gold electrodes. Consistent with earlier findings that utilized different microelectrode chambers for pulse exposure, a single pulse elicited a rapid and transient rise in intracellular calcium by a mechanism that depends on extracellular calcium, which appears to enter the cells largely through voltage-gated calcium channels. In parallel experiments to assess catecholamine release, chromaffin cells were placed into electroporation cuvettes for nanosecond pulse exposure. As measured by high performance liquid chromatography coupled with electrochemical detection, a single pulse elicited an increase in both norepinephrine and epinephrine release that was also dependent on extracellular calcium and involved influx of calcium through voltage gated-calcium channels. Taken together these results indicate that a single nanosecond pulse can act as a stimulus to trigger calcium-dependent catecholamine release from chromaffin cells.