Spatio-temporal resolution of exocytosis from individual cells.

Biophysical events involved in late stages of exocytosis occur at highly localized areas of cells on millisecond and submillisecond time scales. Thus, methodologies with high spatio-temporal resolution are required to achieve measurements at individual secretory cells. Much has been learned about the mechanisms and kinetics of vesicular release through analysis with the carbon fiber microelectrode techniques amperometry and cyclic voltammetry. Coupling of these techniques with other methods such as patch-clamp continues to reveal details of the secretion process. It is now clear that extrusion of the vesicular contents is a more complex process than previously believed. Vesicle-cell fusion, revealed by cell capacitance measurements, is temporally dissociated from secretion measured amperometrically. The stability imparted by interaction and association of vesicle contents at rest results in a rate-limiting extrusion process after full fusion. Furthermore, the presence of partial fusion events and the occurrence of nonquantized release have been revealed with electrochemical tools.