Calcium-dependent synaptic vesicle trafficking underlies indefatigable release at the hair cell afferent fiber synapse

Neuron. 2011 Apr 28;70(2):326-38. doi: 10.1016/j.neuron.2011.01.031.


Sensory hair cell ribbon synapses respond to graded stimulation in a linear, indefatigable manner, requiring that vesicle trafficking to synapses be rapid and nonrate-limiting. Real-time monitoring of vesicle fusion identified two release components. The first was saturable with both release rate and magnitude varying linearly with Ca(2+), however the magnitude was too small to account for sustained afferent firing rates. A second superlinear release component required recruitment, in a Ca(2+)-dependent manner, of vesicles not in the immediate vicinity of the synapse. The superlinear component had a constant rate with its onset varying with Ca(2+) load. High-speed Ca(2+) imaging revealed a nonlinear increase in internal Ca(2+) correlating with the superlinear capacitance change, implicating release of stored Ca(2+) in driving vesicle recruitment. These data, supported by a mass action model, suggest sustained release at hair cell afferent fiber synapse is dictated by Ca(2+)-dependent vesicle recruitment from a reserve pool.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Video-Audio Media

MeSH terms

  • Animals
  • Biophysics
  • Calcium / metabolism*
  • Electric Capacitance
  • Electric Stimulation
  • Exocytosis
  • Hair Cells, Auditory / cytology*
  • Models, Biological
  • Nonlinear Dynamics
  • Patch-Clamp Techniques
  • Synapses / physiology*
  • Synaptic Transmission / physiology*
  • Synaptic Vesicles / physiology*
  • Turtles


  • Calcium