Delay in vesicle fusion revealed by electrochemical monitoring of single secretory events in adrenal chromaffin cells.
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.
Chow
R H
RH
Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.
von Rüden
L
L
Neher
E
E
D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002837:Chromaffin Granules / Q000378:metabolism*; D004553:Electric Conductivity; D005089:Exocytosis / Q000502:physiology*; D008433:Mathematics; D013269:Stochastic Processes
D002395:Catecholamines