A membrane marker leaves synaptic vesicles in milliseconds after exocytosis in retinal bipolar cells

Neuron. 2002 Sep 12;35(6):1085-97. doi: 10.1016/s0896-6273(02)00896-6.


Perhaps synaptic vesicles can recycle so rapidly because they avoid complete exocytosis, and release transmitter through a fusion pore that opens transiently. This view emerges from imaging whole terminals where the fluorescent lipid FM1-43 seems unable to leave vesicles during transmitter release. Here we imaged single, FM1-43-stained synaptic vesicles by evanescent field fluorescence microscopy, and tracked the escape of dye from single vesicles by watching the increase in fluorescence after exocytosis. Dye left rapidly and completely during most or all exocytic events. We conclude that vesicles at this terminal allow lipid exchange soon after exocytosis, and lose their dye even if they connected with the plasma membrane only briefly. At the level of single vesicles, therefore, observations with FM1-43 provide no evidence that exocytosis of synaptic vesicles is incomplete.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Diffusion / drug effects
  • Exocytosis / physiology*
  • Fluorescent Dyes / metabolism
  • Fluorescent Dyes / pharmacology
  • Goldfish
  • Membrane Lipids / metabolism*
  • Presynaptic Terminals / metabolism*
  • Presynaptic Terminals / ultrastructure
  • Protein Transport / physiology
  • Pyridinium Compounds / metabolism
  • Pyridinium Compounds / pharmacology
  • Quaternary Ammonium Compounds / metabolism
  • Quaternary Ammonium Compounds / pharmacology
  • Reaction Time / physiology
  • Retina / metabolism*
  • Retina / ultrastructure
  • Synaptic Membranes / metabolism*
  • Synaptic Membranes / ultrastructure
  • Synaptic Transmission / physiology*
  • Synaptic Vesicles / metabolism*
  • Synaptic Vesicles / ultrastructure


  • FM1 43
  • Fluorescent Dyes
  • Membrane Lipids
  • Pyridinium Compounds
  • Quaternary Ammonium Compounds