Synaptic Vesicle Exocytosis at the Dendritic Lobules of an Inhibitory Interneuron in the Mammalian Retina

Neuron. 2015 Aug 5;87(3):563-75. doi: 10.1016/j.neuron.2015.07.016.


Ribbon synapses convey sustained and phasic excitatory drive within retinal microcircuits. However, the properties of retinal inhibitory synapses are less well known. AII-amacrine cells are interneurons in the retina that exhibit large glycinergic synapses at their dendritic lobular appendages. Using membrane capacitance measurements, we observe robust exocytosis elicited by the opening of L-type Ca(2+) channels located on the lobular appendages. Two pools of synaptic vesicles were detected: a small, rapidly releasable pool and a larger and more slowly releasable pool. Depending on the stimulus, either paired-pulse depression or facilitation could be elicited. During early postnatal maturation, the coupling of the exocytosis Ca(2+)-sensor to Ca(2+) channel becomes tighter. Light-evoked depolarizations of the AII-amacrine cell elicited exocytosis that was graded to light intensity. Our results suggest that AII-amacrine cell synapses are capable of providing both phasic and sustained inhibitory input to their postsynaptic partners without the benefit of synaptic ribbons.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amacrine Cells / metabolism
  • Animals
  • Exocytosis / physiology*
  • Interneurons / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neural Inhibition / physiology*
  • Photic Stimulation / methods
  • Rabbits
  • Retina / cytology
  • Retina / metabolism*
  • Synaptic Vesicles / metabolism*