Extracellular Ca2+per se inhibits quantal size of catecholamine release in adrenal slice chromaffin cells

- Extracellular Ca2+per se inhibited the quantal size of single vesicle release in RACC slice.
- External Ca2+ (2.5 mM) regulates fusion pore kinetics of quantal catecholamine release.
- Removal of external Ca2+ triggered vesicle exocytosis.
- Internal and external Ca2+per se cooperately regulate vescile release probability.
- Quantal size was mainly determined by extracellular Ca2+ in chromaffin cells.