Delay in vesicle fusion revealed by electrochemical monitoring of single secretory events in adrenal chromaffin cells

Nature. 1992 Mar 5;356(6364):60-3. doi: 10.1038/356060a0.


In synapses, a rise in presynaptic intracellular calcium leads to secretory vesicle fusion in less than a millisecond, as indicated by the short delay from excitation to postsynaptic signal. In nonsynaptic secretory cells, studies at high time resolution have been limited by the lack of a detector as fast and sensitive as the postsynaptic membrane. Electrochemical methods may be sensitive enough to detect catecholamines released from single vesicles. Here, we show that under voltage-clamp conditions, stochastically occurring signals can be recorded from adrenal chromaffin cells using a carbon-fibre electrode as an electrochemical detector. These signals obey statistics characteristic for quantal release; however, in contrast to neuronal transmitter release, secretion occurs with a significant delay after short step depolarizations. Furthermore, we identify a pedestal or 'foot' at the onset of unitary events which may represent the slow leak of catecholamine molecules out of a narrow 'fusion pore' before the pore dilates for complete exocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Medulla / cytology
  • Adrenal Medulla / metabolism*
  • Animals
  • Catecholamines / metabolism*
  • Cattle
  • Chromaffin Granules / metabolism*
  • Electric Conductivity
  • Exocytosis / physiology*
  • Mathematics
  • Stochastic Processes


  • Catecholamines