RAPID EXOCYTOSIS IN SINGLE CHROMAFFIN CELLS RECORDED FROM MOUSE ADRENAL SLICES

We report here that brief depolarizations such as action potentials tr igger exocytosis in thin mouse adrenal slices. The secretory rates obt ained in membrane capacitance recordings from chromaffin cells in slic es are faster than those observed in isolated cells. Fast exocytosis i n slices is attributable to the rapid release of a small pool of vesic les. The pool recovers from depletion with a time constant of 10 sec. Recruitment of the rapidly released vesicles is strongly hindered by t he fast Ca2+ chelator BAPTA and much less by the slower chelator EGTA. We suggest that these vesicles are located in close proximity to Ca2 channels. Spatial coupling of Ca2+ entry and exocytosis may be sensit ive to cell isolation and culture.