Membrane Capacitance Measurements of Stimulus-Evoked Exocytosis in Adrenal Chromaffin Cells

Research using membrane capacitance (C_m) measurements in adrenal chromaffin cells has transformed our understanding of the molecular mechanisms controlling regulated exocytosis. This is in part due to the exquisite temporal resolution of the technique, and the possibility of combining quantification of exo-/endocytosis at the whole-cell level, with the ability to simultaneously monitor and control the calcium signals triggering vesicle fusion. In this regard, experiments performed with C_m measurements complement amperometry experiments that give a measure of secreted transmitter and the behavior of the fusion pore, and fluorescent microscopy studies used to monitor vesicle and protein dynamics in imaged regions of the cell. In this chapter, we provide a detailed account of the methodology used to perform whole-cell patch clamp measurements of C_m in combination with voltage-clamp recordings of voltage-gated calcium channels to quantify stimulus-secretion coupling in chromaffin cells. Stimulus protocols developed for investigation of functionally distinct releasable vesicle pools are also described.