Mammalian rod terminal: architecture of a binary synapse

Neuron. 1995 Mar;14(3):561-9. doi: 10.1016/0896-6273(95)90312-7.


The mammalian rod synapse transmits a binary signal (one photon or none) using tonic, rapid exocytosis. We constructed a quantitative, physical model of the synapse. Presynaptically, a single, linear active zone provides docking sites for approximately 130 vesicles, and a "ribbon" anchored to the active zone provides a depot for approximately 640 vesicles. Postsynaptically, 4 processes invaginate the terminal: 2 (known to have low affinity glutamate receptors) lie near the active zone (16 nm), and 2 (known to have high affinity glutamate receptors) lie at a distance (130-640 nm). The presynaptic structure seems designed to minimize fluctuations in tonic rate owing to empty docking sites, whereas the postsynaptic geometry may permit 1 vesicle to evoke an all-or-none response at all 4 postsynaptic processes.

Publication types

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

MeSH terms

  • Animals
  • Cats
  • Darkness
  • Light
  • Microscopy, Electron
  • Models, Neurological
  • Models, Structural
  • Retinal Rod Photoreceptor Cells / physiology
  • Retinal Rod Photoreceptor Cells / ultrastructure*
  • Synapses / physiology
  • Synapses / ultrastructure*