Exo-endocytosis in isolated peptidergic nerve terminals occurs in the sub-second range.
Exo- and endocytotic processes induced by depolarization of isolated neurosecretory nerve terminals show a close temporal correlation, which suggests a short time of integration of the neurosecretory granule membrane with the plasma membrane. In order to determine minimal time requirements for exocytosis-coupled endocytosis to occur, we have analyzed by electron microscopy uptake of horseradish peroxidase (HRP) as a fluid phase marker at the onset of depolarization. We have applied rapid mixing and sampling (quenched flow) to assess events in sub-second time periods after stimulation. A significant number of labelled endocytotic vacuoles was observed during the first second of depolarization. This number then further increased by a factor of about 2 (within 5 s) and 4 (within 50 s). Thus, as for exocytosis, the rate of endocytosis decreased considerably during prolonged stimulation. These data indicate i) that a substantial proportion of secretory granules undergoes exocytosis very shortly after stimulation, and ii) that, following exocytosis, the minimal time required for consecutive membrane retrieval is in the sub-second range.
Knoll
G
G
C.N.R.S., Centre de Neurochimie-UPR 416, Strasbourg, France.
Plattner
H
H
Nordmann
J J
JJ
D000818:Animals; D003594:Cytoplasmic Granules / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000502:physiology* / Q000648:ultrastructure; D009479:Neuropeptides / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D014617:Vacuoles / Q000502:physiology
D009479:Neuropeptides