Two modes of exocytosis at hippocampal synapses revealed by rate of FM1-43 efflux from individual vesicles.
We have examined the kinetics by which FM1-43 escapes from individual synaptic vesicles during exocytosis at hippocampal boutons. Two populations of exocytic events were observed; small amplitude events that lose dye slowly, which made up more than half of all events, and faster, larger amplitude events with a fluorescence intensity equivalent to single stained synaptic vesicles. These populations of destaining events are distinct in both brightness and kinetics, suggesting that they result from two distinct modes of exocytosis. Small amplitude events show tightly clustered rate constants of dye release, whereas larger events have a more scattered distribution. Kinetic analysis of the association and dissociation of FM1-43 with membranes, in combination with a simple pore permeation model, indicates that the small, slowly destaining events may be mediated by a narrow approximately 1-nm fusion pore.
Richards
David A
DA
Department of Physiology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Bai
Jihong
J
Chapman
Edwin R
ER
D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis; D005456:Fluorescent Dyes / Q000378:metabolism / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007700:Kinetics; D008081:Liposomes; D008555:Melitten / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D008959:Models, Neurological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011233:Precipitin Tests; D017729:Presynaptic Terminals / Q000378:metabolism; D011726:Pyridinium Compounds / Q000378:metabolism / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology; D050683:R-SNARE Proteins; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism*; D050857:Synaptotagmins
D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D005456:Fluorescent Dyes; D008081:Liposomes; D008555:Melitten; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D050683:R-SNARE Proteins; D016194:Receptors, N-Methyl-D-Aspartate; D050857:Synaptotagmins; C073804:FM1 43